5 The main task of the lexical scanner is to convert a stream of
6 characters into a stream of tokens. The tokens are then typically
7 used by a parser to extract the syntactic structure.
9 The stream of characters are assumed to be in memory identified by a
10 linked list of blocks, such as provided by the "[mdcode][]" literate
11 program extractor. A single token may never cross a block boundary.
18 The text is assumed to be UTF-8 though some matching assumes the
19 ASCII subset. If the text provided does not conform to UTF-8 an error
20 will be reported and some number of bytes will be skipped.
25 #include <unicode/uchar.h>
27 Tokens are returned by successive calls to the main interface
28 function: `token_next()` which has a `state` structure to keep track
29 of where it is up to. Each token carries not just a numeric
30 identifier but also the code block, the line and character within that
31 block, and the actual start and length using the `struct text` from
37 struct code_node *node;
48 ###### exported functions
49 struct token token_next(struct token_state *state);
52 struct token token_next(struct token_state *state)
63 The `line` and `col` offsets are useful for reporting errors.
64 The `txt` provides the content when that is important.
66 ### Token types and configuration ##
68 The scanner is not completely general, yet not completely specified.
69 There are a fixed set of token types, though particular tokens within
70 those types can be distinguish via configuration.
72 Most token types may be explicitly ignored, as typically comments
73 would be. The exact consequence of ignoring each token type varies
78 int ignored; // bit set of ignored tokens.
79 ## token config parameters
83 struct token_config *conf;
85 ###### token_next init
86 int ignored = state->conf->ignored;
89 The different tokens are numbers, words, marks, strings, comments,
90 newlines, EOF, and indents, each of which is examined in detail below.
92 There are various cases where no token can be found in part of the
93 input. All of these will be reported as an `TK_error` token.
95 It is possible to declare a number of strings which form distinct
96 tokens (rather than being grouped as e.g. 'word'). These are given
97 token numbers from `TK_reserved` upwards.
108 Numbers are the messiest tokens to parse, primarily because they can
109 contain characters that also have meaning outside of number and,
110 particularly, immediately after numbers.
112 The obvious example is the '`-`' sign. It can come inside a number for
113 a negative exponent, or after a number as a subtraction operator. To
114 be sure we have parsed as best as possible we need to only allow the
115 '`-`' inside a number if it is after an exponent character. This can be
116 `e` or `p` (for hex exponents), but `e` can also be a hexadecimal
117 digit, so we don't allow '`-`' after just any `e`.
119 To make matters worse, our language designer has decided to experiment
120 with allowing commas to be used as the decimal indicator, and spaces
121 to be used to separate groups of digits in large numbers. Both of
122 these can reasonably be restricted to appear between two digits, so we
123 have to add that condition to our tests.
125 So we cannot just treat numbers as starting with a digit and being
126 followed by some set of characters. We need more structure than that.
130 - Numbers must start with a digit.
131 - If the first digit is zero, the next character must be a base
132 signifier (one of `xob`) or a decimal marker (`.` or `,`).
133 In the first case the first `p` or `P` may be followed by a sign.
134 - If the number doesn't start with `0` followed by one of `xob`, the
135 first `e` may be followed by a sign.
136 - Any digit or hex digit may be followed by a space or underscore
137 providing that the subsequence character is also a (hex) digit.
138 This rule will require an extra level of 'unget' to be
139 supported when handling characters.
140 - Otherwise any digits or ASCII letters are allowed. We do not at
141 this point check that the digits given are permitted by the base.
142 That will happen when the token is converted to a number.
144 To allow easy configuration, the various non alphanumeric characters
145 are only permitted if they are listed in a configuration parameter.
147 ###### token config parameters
150 Note that numbers may not start with a period, so `.75` is not a
151 number. This is not the norm, but is not unheard of. Excluding these
152 numbers simplifies the rule at very little cost.
157 If TK_number is ignored, digits will result in an error unless they
158 are declared to be a start character for words.
166 if (iswdigit(ch) && !(ignored & (1<<TK_number))) {
167 int prev_special = 0;
169 int decimal_mark = 0;
171 wchar_t ch2 = get_char(state);
172 if (strchr("xobXOB", ch2) != NULL)
180 if (ch == 'e' || ch == 'E')
184 if (ch == 'p' || ch == 'P')
188 save_unget_state(state);
189 ch = get_char(state);
194 if (ch == '+' || ch == '-') {
199 if (ch == '.' || ch == ',') {
205 /* Don't allow that special char,
208 restore_unget_state(state);
211 if (strchr(state->conf->number_chars, ch)) {
215 /* non-number char */
218 /* We seem to have a "number" token */
220 close_token(state, &tk);
226 Words start with a "start" character followed by the longest
227 sequence of "continue" characters. The Unicode ID_START and
228 ID_CONTINUE sets are always permitted, but other ASCII characters
229 can be added to these sets.
231 ###### token config parameters
235 ###### internal functions
236 static int is_word_start(wchar_t ch, struct token_config *conf)
238 return iswalpha(ch) ||
239 strchr(conf->word_start, ch) != NULL ||
240 u_hasBinaryProperty(ch, UCHAR_ID_START);
243 static int is_word_continue(wchar_t ch, struct token_config *conf)
245 return iswalnum(ch) ||
246 strchr(conf->word_cont, ch) != NULL ||
247 u_hasBinaryProperty(ch, UCHAR_ID_CONTINUE);
250 Words can be either known or unknown. Known words are referred to as
251 "reserved words" and get a unique token number. Unknown words are
252 "identifiers" and are syntactically a single token.
257 A list of known words must be provided. This list is shared with the
258 "marks" which are described next. The list must be lexically sorted
259 and the length of the list must be given (`known_count`).
260 Tokens matching these known words are reported as the index of the
261 list added to `TK_reserved`.
263 ###### token config parameters
264 const char **words_marks;
269 if (is_word_start(ch, state->conf)) {
271 /* A word: identifier or reserved */
273 ch = get_char(state);
274 while (is_word_continue(ch, state->conf));
276 close_token(state, &tk);
278 if (ignored & (1<<TK_ident))
280 n = find_known(state->conf, tk.txt);
282 tk.num = TK_reserved + n;
288 Marks are generally one or more punctuation marks joined together. It
289 would be nice to use the term "symbol" for these, but that causes
290 confusion in a subsequent discussion of the grammar, which has terminal
291 symbols and non-terminal symbols which are conceptually quite
292 different. So strings of punctuation characters will be marks.
294 A "mark" consists of ASCII characters that are not white space, are not
295 "start" characters for words, and are not digits.
296 These will collectively be called mark characters.
298 ###### internal functions
299 static int is_mark(wchar_t ch, struct token_config *conf)
304 strchr(conf->word_start, ch) == NULL;
307 As with words, there can be known and unknown marks, though the rules
308 are slightly different.
310 Two marks do not need to be separated by a non-mark characters. This
311 is different from words which do need to be separated by at least one
312 non-continue character.
314 The scanner will normally prefer longer sequences of mark characters,
315 but will more strongly prefer known marks over unknown marks. So if
316 it finds a known mark where adding one more character does not result
317 in a known mark, it will return that first known mark.
319 If no known mark is found we will test against strings and comments
320 below before giving up and assuming an unknown mark.
322 If an unknown mark contains a quote character or a comment marker, and
323 that token is not being ignored, then we terminate the unknown mark
324 before that quote or comment. This ensure that an unknown mark
325 immediately before a string is handled correctly.
327 If `TK_mark` is ignored, then unknown marks as returned as an error.
332 Known marks are included in the same list as the list of known words.
336 while (is_mark(ch, state->conf)) {
339 close_token(state, &tk);
340 n = find_known(state->conf, tk.txt);
342 tk.num = TK_reserved + n;
343 else if (tk.num != TK_error) {
344 /* found a longest-known-mark */
346 close_token(state, &tk);
350 save_unget_state(state);
351 ch = get_char(state);
352 if (!(ignored && (1<<TK_string)) && is_quote(ch))
356 if (prev == '/' && ch == '/' && tk.txt.len > 1) {
357 restore_unget_state(state);
360 if (prev == '/' && ch == '*' && tk.txt.len > 1) {
361 restore_unget_state(state);
366 if (tk.num != TK_error) {
367 close_token(state, &tk);
371 If we don't find a known mark, we will check for strings and comments
372 before assuming that we have an unknown mark
381 if (ignored & (1<<TK_mark))
390 Strings start with one of single quote, double quote, or back quote
391 and continue until a matching character on the same line. Any of
392 these characters can be included in the list of known marks and then
393 they will not be used for identifying strings.
395 Immediately following the close quote one or two ASCII letters may
396 appear. These are somewhat like the arbitrary letters allowed in
397 "Numbers" above. They can be used by the language in various ways.
399 If 3 identical quote characters appear in a row and are
400 followed by a newline, then this forms a multi-line string which
401 continues until an identical triple quote appears on a line preceded
402 only by whitespace and followed immediately by 0-2 ASCII letters and a newline.
404 Multi-line strings may not extend beyond the end of the `code_node` in
407 Normal strings and multi-line strings are encoded as two different
414 ###### internal functions
415 static int is_quote(wchar_t ch)
417 return ch == '\'' || ch == '"' || ch == '`';
420 #### Multi-line strings
422 The multi-line string is checked for first. If they are being
423 ignored, we fall through and treat a triple quote as an empty string
424 followed by the start of a new string.
427 if (tk.txt.len == 3 &&
428 !(ignored & (1 << TK_multi_string)) &&
429 is_quote(tk.txt.txt[0]) &&
430 memcmp(tk.txt.txt, tk.txt.txt+1, 2) == 0 &&
431 is_newline(tk.txt.txt[3])) {
433 wchar_t first = tk.txt.txt[0];
436 while (!at_eon(state) && qseen < 3) {
437 ch = get_char(state);
438 if (is_newline(ch)) {
441 } else if (at_sol && ch == first) {
443 } else if (ch != ' ' && ch != '\t') {
449 /* Hit end of node - error.
450 * unget so the newline is seen,
451 * but return rest of string as an error.
454 close_token(state, &tk);
458 /* 2 letters are allowed */
459 ch = get_char(state);
461 ch = get_char(state);
463 ch = get_char(state);
464 /* Now we must have a newline, but we don't return it
467 close_token(state, &tk);
468 tk.num = TK_multi_string;
474 #### Single-line strings
476 The sequence of marks collected may be more than a single-line
477 string, so we reset to the start and collect characters until
478 we find a close quote or a newline.
480 If `TK_string` is ignored, then quote characters will appear as `TK_mark`s.
483 if (tk.txt.len && is_quote(tk.txt.txt[0]) &&
484 !(ignored & (1<<TK_string))) {
485 wchar_t first = tk.txt.txt[0];
486 reset_token(state, &tk);
489 ch = get_char(state);
490 while (ch != first && !is_newline(ch));
492 if (is_newline(ch)) {
496 close_token(state, &tk);
502 Single line comments may start with '`//`' or '`#`' providing that these
503 are not known marks. They continue to the end of the line.
505 Block comments start with '`/*`' if this is not a known mark. They
506 continue to the first occurrence of '`*/`' and may not contain any
507 occurrence of '`/*`'.
509 Block comments can be wholly within one line or can continue over
510 multiple lines. The multi-line version should be followed immediately
511 by a newline. The Linux kernel contains over 285000 multi-line
512 comments are only 34 are followed by characters other than white space
513 (which should be removed) or a backslash (only needed in macros). So
514 it would not suffer from this rule.
516 These two comment types are reported as two separate token types, and
517 consequently can be ignored separately. When ignored a comment is
518 still parsed, but is discarded.
524 ###### internal functions
525 static int is_line_comment(struct text txt)
527 return (txt.len >= 1 && txt.txt[0] == '#') ||
528 (txt.len >= 2 && txt.txt[0] == '/' &&
532 static int is_block_comment(struct text txt)
534 return txt.len >= 2 && txt.txt[0] == '/' &&
538 #### Single line comments
540 A single-line comment continues up to, but not including the newline.
544 if (is_line_comment(tk.txt)) {
545 while (!is_newline(ch))
546 ch = get_char(state);
548 close_token(state, &tk);
549 tk.num = TK_line_comment;
550 if (ignored & (1 << TK_line_comment))
557 The token text collected so far could exceed the comment, so we need
560 If we find an embedded `/*` we reset to just before the '/' and report
561 an error. That way the next thing to be parsed will be the rest of
562 the comment. This requires a double unget, so we need to save/restore
563 the unget state (explained later).
567 if (is_block_comment(tk.txt)) {
570 reset_token(state, &tk);
573 save_unget_state(state);
574 ch = get_char(state);
576 while (!at_eon(state) &&
577 (prev != '/' || ch != '*') &&
578 (prev != '*' || ch != '/')) {
582 save_unget_state(state);
583 ch = get_char(state);
585 close_token(state, &tk);
591 /* embedded. Need to unget twice! */
592 restore_unget_state(state);
597 tk.num = TK_block_comment;
598 if (newlines && !(ignored & (1<<TK_newline))) {
599 /* next char must be newline */
600 ch = get_char(state);
605 if (tk.num == TK_error ||
606 !(ignored & (1 << TK_block_comment)))
611 ### Indents, Newlines, and White Space.
613 Normally white space is ignored. However newlines can be important as
614 can indents, which are either after a newline or at the start of a
615 node (detected by `at_son()`);
617 ###### exported functions
618 static inline int is_newline(wchar_t ch)
620 return ch == '\n' || ch == '\f' || ch == '\v';
624 if (ch <= ' ' && !is_newline(ch)
628 If a line starts with more white-space than the previous non-blank
629 line - or if the first non-blank line in the document starts with any
630 white-space - then an "IN" is reported at the start of the line.
632 Before the next non-blank line which starts with less white space, or
633 at the latest at the end of the document, a matching "OUT" token
634 is reported. There will always be an exact match between "IN" and
637 It is possible for "OUT" to be followed (almost) immediately by an
638 "IN". This happens if, for example, the indent of three consecutive
639 lines are 0, 8, 4 spaces. Before the second line we report an
640 "IN". Before the third line we must report an "OUT", as 4 is less
641 than 8, then also an Ident as 4 is greater than 0.
647 For the purpose of measuring the length of white space, a tab adds at
648 least one space, and rounds up to a multiple of 8.
650 ###### exported functions
651 static inline int indent_tab(int indent)
656 We need to track the current levels of indent. This requires some
657 sort of stack as indent levels are pushed on and popped off. In
658 practice this stack is unlikely to often exceed 5 so we will used a
659 fixed stack of 20 indent levels. More than this will be silently
664 int indent_sizes[20];
668 Newlines can optionally be reported. Newlines within a block comment
669 or a multi-line string are not reported separately, but each of these
670 must be followed immediately by a newline so these constructs cannot
671 hide the fact that a newline was present.
673 When indents are being reported, the Newline which would normally be
674 reported immediately before the "IN" is delayed until after the
675 matching "OUT". This makes an indented section act like a
676 continuation of the previous line to some extent.
678 A blank line would normally be reported simply as two consecutive Newline
679 tokens. However if the subsequent line is indented (and indents are being
680 reported) then the right thing to do is less obvious as Newlines should be
681 delayed - but how many Newlines?
683 The approach we will take is to report the extra Newlines immediately after
684 the IN token, so the blank line is treated as though it were an indented
690 If we find a newline or white space at the start of a block, we keep
691 collecting spaces, tabs, and newlines until we find some real text.
692 Then depending on the indent we generate some number of tokens. These
693 will be a sequence of "Newline OUT" pairs representing a decrease
694 in indent, then either a Newline or an IN depending on whether the
695 next line is indented, then zero or more Newlines representing all the
696 blank lines that have been skipped.
698 When a Newline leads to the next block of code there is a question of
699 whether the various Newline and OUT/IN tokens should appear to
700 pbelong to the earlier or later block. This is addressed by processing
701 the tokens in two stages based on the relative indent levels of the
702 two blocks (each block has a base indent to which the actual indents
705 Any "Newline OUT" pairs needed to reduce the current indent to the
706 maximum of the base indents of the old and new blocks are generated
707 against the old block. Then if the next block does not have an
708 increased indent, one more "Newline" is generated.
710 If further "Newline OUT" pairs are needed to get to the indent
711 level of the 'next' block, they are generated against that block,
712 though the first Newline is suppressed (it having already been
715 Finally the Newline or IN for the first line of the new block is
716 generated, unless the Newline needs to be suppressed because it
717 appeared at the end of the previous block.
719 This means that a block may start with an OUT or an IN, but
720 will only start with a Newline if it actually starts with a blank
723 We will need to represent in the `token_state` where in this sequence
724 of delayed tokens we are. As `state.col` records the target indent we
725 don't need to record how many OUTs or INs are needed. We do
726 need to record the number of blank lines, and which of Newline and
727 OUT is needed next in the initial sequence of pairs.
729 For this we store one more than the number of blank lines as
730 `delayed_lines` and a flag for `out_next`.
737 Generating these tokens involve two separate pieces of code.
739 Firstly we need to recognise white space and count the indents and
740 newlines. These are recorded in the above state fields.
742 Separately we need, on each call to `token_next`, we need to check if
743 there are some delayed tokens and if so we need to advance the state
744 information and return one token.
747 if (is_newline(ch) || (at_son(state) && ch <= ' ')) {
749 int was_son = at_son(state);
750 if (ignored & (1<<TK_in)) {
753 if (ignored & (1<<TK_newline))
756 close_token(state, &tk);
759 // Indents are needed, so check all white space.
760 while (ch <= ' ' && !at_eon(state)) {
763 ch = get_char(state);
767 if (state->node->next &&
768 state->node->next->indent > state->node->indent)
769 state->col = state->node->next->indent;
771 state->col = state->node->indent;
774 state->delayed_lines = newlines;
775 state->out_next = was_son;
776 state->check_indent = 1;
781 ###### delayed tokens
783 if (state->check_indent || state->delayed_lines) {
784 if (state->col < state->indent_sizes[state->indent_level]) {
785 if (!state->out_next &&
786 !(ignored & (1<<TK_newline))) {
791 state->indent_level -= 1;
796 if (state->col > state->indent_sizes[state->indent_level] &&
797 state->indent_level < sizeof(state->indent_sizes)-1) {
798 state->indent_level += 1;
799 state->indent_sizes[state->indent_level] = state->col;
800 state->delayed_lines -= 1;
804 state->check_indent = 0;
805 if (state->delayed_lines && !(ignored & (1<<TK_newline))) {
807 state->delayed_lines -= 1;
810 state->delayed_lines = 0;
816 After the last newline in the file has been processed, a special
817 end-of-file token will be returned. any further attempts to get more
818 tokens will continue to return the same end-of-file token.
830 ### Unknown Marks, or errors.
832 We have now handled all the possible known mark-like tokens.
833 If the token we have is not empty and `TK_mark` is allowed,
834 we have an unknown mark, otherwise this must be an error.
837 /* one unknown character */
838 close_token(state, &tk);
842 ## Tools For The Task
844 You may have noticed that are few gaps we left in the above -
845 functions used without first defining them. Doing so above would have
848 ### Character by character
850 As we walk through the various `code_node`s we need to process whole
851 Unicode codepoints, and keep track of which line and column we are on.
852 We will assume for now that any printing character uses one column,
853 though that is not true in general.
855 As the text in a `code_node` may include an indent that identifies it as
856 being code, we need to be careful to strip that. The `code_node` has
857 a flag that tells us whether or not we need to strip.
863 struct code_node *node;
868 ###### internal functions
870 static void do_strip(struct token_state *state)
872 if (state->node->needs_strip) {
874 while (n && state->node->code.txt[state->offset] == ' ') {
878 while (n == 4 && state->node->code.txt[state->offset] == '\t') {
885 static wint_t get_char(struct token_state *state)
891 if (state->node == NULL)
893 if (state->node->code.len <= state->offset) {
895 state->node = state->node->next;
896 while (state->node && state->node->code.txt == NULL);
898 if (state->node == NULL)
901 state->line = state->node->line_no;
902 state->col = state->node->indent;
907 memset(&mbstate, 0, sizeof(mbstate));
909 n = mbrtowc(&next, state->node->code.txt + state->offset,
910 state->node->code.len - state->offset,
912 if (n == -2 || n == 0) {
913 /* Not enough bytes - not really possible */
915 state->offset = state->node->code.len;
916 } else if (n == -1) {
919 next = 0x7f; // an illegal character
925 } else if (is_newline(next)) {
927 state->col = state->node->indent;
929 } else if (next == '\t') {
930 state->col = indent_tab(state->col);
935 We will sometimes want to "unget" the last character as it needs to be
936 considered again as part of the next token. So we need to store a
937 'previous' version of all metadata.
944 ###### before get_char
945 state->prev_offset = state->offset;
946 state->prev_line = state->line;
947 state->prev_col = state->col;
949 ###### internal functions
951 static void unget_char(struct token_state *state)
954 state->offset = state->prev_offset;
955 state->line = state->prev_line;
956 state->col = state->prev_col;
960 We occasionally need a double-unget, particularly for numbers and
961 block comments. We don't impose this cost on all scanning, but
962 require those code sections that need it to call `save_unget_state`
963 before each `get_char`, and then `restore_unget_state` when a
964 double-unget is needed.
971 ###### internal functions
972 static void save_unget_state(struct token_state *state)
974 state->prev_offset2 = state->prev_offset;
975 state->prev_line2 = state->prev_line;
976 state->prev_col2 = state->prev_col;
979 static void restore_unget_state(struct token_state *state)
981 state->prev_offset = state->prev_offset2;
982 state->prev_line = state->prev_line2;
983 state->prev_col = state->prev_col2;
986 At the start of a token we don't want to be at the end of a code block
987 if we can help it. To avoid this possibility, we 'get' and 'unget' a
988 single character. This will move into the next non-empty code block
989 and leave the current pointer at the start of it.
991 This has to happen _after_ dealing with delayed tokens as some of them
992 must appear in the previous node. When we do this, we need to reset
993 the data in the token.
995 ###### delayed tokens
999 tk.node = state->node;
1001 tk.txt.txt = state->node->code.txt + state->offset;
1002 tk.line = state->line;
1003 tk.col = state->col;
1009 The current token is initialized to line up with the first character
1010 that we 'get' for each token. When we have, or might have, a full
1011 token we can call `close_token` to set the `len` of the token
1012 appropriately. This can safely be called multiple times.
1014 Finally we occasionally (for single-line strings and block comments)
1015 need to reset to the beginning of the current token as we might have
1016 parsed too much already. For that there is `reset_token`.
1019 tk.node = state->node;
1021 tk.txt.txt = state->node->code.txt + state->offset;
1022 tk.line = state->line;
1023 tk.col = state->col;
1026 ###### internal functions
1028 static void close_token(struct token_state *state,
1031 tk->txt.len = (state->node->code.txt + state->offset)
1035 static void reset_token(struct token_state *state, struct token *tok)
1037 state->prev_line = tok->line;
1038 state->prev_col = tok->col;
1039 state->prev_offset = tok->txt.txt - state->node->code.txt;
1045 Tokens make not cross into the next `code_node`, and some tokens can
1046 include the newline at the and of a `code_node`, we must be able to
1047 easily check if we have reached the end. Equally we need to know if
1048 we are at the start of a node, as white space is treated a little
1051 ###### internal functions
1053 static int at_son(struct token_state *state)
1055 return state->offset == 0;
1058 static int at_eon(struct token_state *state)
1060 // at end-of-node ??
1061 return state->node == NULL ||
1062 state->offset >= state->node->code.len;
1065 ### Find a known word
1067 As the known-word list is sorted we can use a simple binary search.
1068 Following the pattern established in "mdcode", we will use a `struct
1069 text` with start and length to represent the code fragment we are
1072 ###### internal functions
1073 static int find_known(struct token_config *conf, struct text txt)
1076 int hi = conf->known_count;
1078 while (lo + 1 < hi) {
1079 int mid = (lo + hi) / 2;
1080 int cmp = strncmp(conf->words_marks[mid],
1082 if (cmp == 0 && conf->words_marks[mid][txt.len])
1089 if (strncmp(conf->words_marks[lo],
1090 txt.txt, txt.len) == 0
1091 && conf->words_marks[lo][txt.len] == 0)
1097 ### Bringing it all together
1099 Now we have all the bits there is just one section missing: combining
1100 all the token parsing code into one block.
1102 The handling of delayed tokens (Newlines, INs, OUTs) must come
1103 first before we try getting another character.
1105 Then we parse all the test, making sure that we check for known marks
1106 before strings and comments, but unknown marks after strings and comments.
1108 This block of code will either return a token, or will choose to
1109 ignore one, in which case it will `continue` around to the top of the
1115 ch = get_char(state);
1124 As well as getting tokens, we need to be able to create the
1125 `token_state` to start with, and discard it later.
1130 ###### main functions
1131 struct token_state *token_open(struct code_node *code, struct
1134 struct token_state *state = malloc(sizeof(*state));
1135 memset(state, 0, sizeof(*state));
1137 state->line = code->line_no;
1138 state->col = code->indent;
1143 void token_close(struct token_state *state)
1148 ###### exported functions
1149 struct token_state *token_open(struct code_node *code, struct
1150 token_config *conf);
1151 void token_close(struct token_state *state);
1155 Getting tokens is the main thing but it is also useful to be able to
1156 print out token information, particularly for tracing and testing.
1158 Known tokens are printed verbatim. Other tokens are printed as
1159 `type(content)` where content is truncated to a given number of characters.
1161 The function for printing a truncated string (`text_dump`) is also exported
1162 so that it can be used to tracing processed strings too.
1167 ###### exported functions
1168 void token_trace(FILE *f, struct token tok, int max);
1169 void text_dump(FILE *f, struct text t, int max);
1171 ###### main functions
1173 void text_dump(FILE *f, struct text txt, int max)
1180 for (i = 0; i < max; i++) {
1181 char c = txt.txt[i];
1182 if (c < ' ' || c > '~')
1183 fprintf(f, "\\x%02x", c & 0xff);
1187 fprintf(f, "%c", c);
1193 void token_trace(FILE *f, struct token tok, int max)
1195 static char *types[] = {
1196 [TK_ident] = "ident",
1198 [TK_number] = "number",
1199 [TK_string] = "string",
1200 [TK_multi_string] = "mstring",
1201 [TK_line_comment] = "lcomment",
1202 [TK_block_comment] = "bcomment",
1205 [TK_newline] = "newline",
1207 [TK_error] = "ERROR",
1211 default: /* known word or mark */
1212 fprintf(f, "%.*s", tok.txt.len, tok.txt.txt);
1218 /* No token text included */
1219 fprintf(f, "%s()", types[tok.num]);
1225 case TK_multi_string:
1226 case TK_line_comment:
1227 case TK_block_comment:
1229 fprintf(f, "%s(", types[tok.num]);
1230 text_dump(f, tok.txt, max);
1236 ### And there we have it
1238 We now have all the library functions defined for reading and printing
1239 tokens. Now we just need C files to store them, and a mk file to make them.
1241 ###### File: scanner.h
1243 ## exported functions
1245 ###### File: libscanner.c
1247 #include "scanner.h"
1249 ## internal functions
1252 ###### File: scanner.mk
1256 scanner.mk scanner.h libscanner.c : scanner.mdc
1259 libscanner.o : libscanner.c
1260 $(CC) $(CFLAGS) -c libscanner.c
1262 ## Processing numbers
1264 Converting a `TK_number` token to a numerical value is a slightly
1265 higher level task than lexical analysis, and slightly lower than
1266 grammar parsing, so put it here - as an index if you like.
1268 Importantly it will be used by the same testing rig that is used for
1269 testing the token scanner.
1271 The numeric value that we will convert all numbers into is the `mpq_t`
1272 from the GNU high precision number library "libgmp".
1274 ###### number includes
1278 Firstly we need to be able to parse a string of digits in a given base
1279 and possibly with a decimal marker. We store this in an `mpz_t`
1280 integer and report the number of digits after the decimal mark.
1282 On error we return zero and ensure that the 'mpz_t' has been freed, or
1283 had never been initialised.
1285 ###### number functions
1287 static int parse_digits(mpz_t num, struct text tok, int base,
1290 /* Accept digits up to 'base', ignore '_' and
1291 * ' ' if they appear between two legal digits,
1292 * and if `placesp` is not NULL, allow a single
1293 * '.' or ',' and report the number of digits
1295 * Return number of characters processed (p),
1296 * or 0 if something illegal was found.
1299 int decimal = -1; // digits after marker
1300 enum {Digit, Space, Other} prev = Other;
1303 for (p = 0; p < tok.len; p++) {
1305 char c = tok.txt[p];
1307 if (c == '_' || c == ' ') {
1313 if (c == '.' || c == ',') {
1316 if (!placesp || decimal >= 0)
1324 else if (isupper(c))
1326 else if (islower(c))
1337 mpz_mul_ui(num, num, base);
1341 mpz_add_ui(num, num, dig);
1360 ###### number includes
1363 To parse a full number we need to consider the optional base, the
1364 mantissa, and the optional exponent. We will treat these one at a
1367 The base is indicated by a letter after a leading zero, which must be
1368 followed by a base letter or a period. The base also determines the
1369 character which will mark an exponent.
1377 if (tok.txt[0] == '0' && tok.len > 1) {
1379 switch(tok.txt[1]) {
1410 // another digit is not permitted
1414 // must be decimal marker or trailing
1415 // letter, which are OK;
1422 After the base is the mantissa, which may contain a decimal mark, so
1423 we need to record the number of places. We won't impose the number of
1424 places until we have the exponent as well.
1431 ###### parse mantissa
1433 d = parse_digits(mant, tok, base, &places);
1439 mpq_set_z(num, mant);
1442 After the mantissa number may come an exponent which may be positive
1443 or negative. We assume at this point that we have seen the exponent
1451 ###### parse exponent
1453 if (tok.txt[0] == '+') {
1456 } else if (tok.txt[0] == '-') {
1462 d = parse_digits(exp, tok, 10, NULL);
1467 if (!mpz_fits_slong_p(exp)) {
1472 lexp = mpz_get_si(exp) * esign;
1478 Now that we have the mantissa and the exponent we can multiply them
1479 together, also allowing for the number of digits after the decimal
1482 For base 10, we simply subtract the decimal places from the exponent.
1483 For the other bases, as the exponent is alway based on 2, even for
1484 octal and hex, we need a bit more detail.
1485 We then recover the sign from the exponent, as division is quite
1486 different from multiplication.
1488 ###### calc exponent
1507 Imposing the exponent on the number is also very different for base 10
1508 than for the others. For the binary shift `gmp` provides a simple
1509 function. For base 10 we use something like Russian Peasant
1512 ###### calc exponent
1516 mpq_set_ui(tens, 10, 1);
1520 mpq_mul(num, num, tens);
1522 mpq_div(num, num, tens);
1527 mpq_mul(tens, tens, tens);
1532 mpq_mul_2exp(num, num, lexp);
1534 mpq_div_2exp(num, num, lexp);
1537 Now we are ready to parse a number: the base, mantissa, and exponent.
1538 If all goes well we check for the possible trailing letters and
1539 return. Return value is 1 for success and 0 for failure.
1542 ###### number functions
1543 int number_parse(mpq_t num, char tail[3], struct text tok)
1550 if (tok.len > 1 && (tok.txt[0] == expc ||
1551 tok.txt[0] == toupper(expc))) {
1558 for (i = 0; i < 2; i++) {
1561 if (!isalpha(tok.txt[i]))
1563 tail[i] = tok.txt[i];
1573 Number parsing goes in `libnumber.c`
1575 ###### File: libnumber.c
1583 ###### File: number.h
1584 int number_parse(mpq_t num, char tail[3], struct text tok);
1586 ###### File: scanner.mk
1588 libnumber.o : libnumber.c
1589 $(CC) $(CFLAGS) -c libnumber.c
1591 ## Processing strings
1593 Both `TK_string` and `TK_multi_string` require post-processing which
1594 can be one of two types: literal or with escapes processed.
1595 Even literal processing is non-trivial as the file may contain indents
1596 which need to be stripped.
1598 Errors can only occur when processing escapes. Any unrecognised
1599 character following the escape character will cause an error.
1601 Processing escapes and striping indents can only make the string
1602 shorter, not longer, so we allocate a buffer which is the same size as
1603 the string and process into that.
1605 To request escape processing, we pass the character we want to use for
1606 quoting, usually '`\`'. To avoid escape processing we pass a zero.
1609 int string_parse(struct token *tok, char escape,
1610 struct text *str, char tail[3])
1613 struct text t = tok->txt;
1617 if (tok->num == TK_string) {
1622 str->txt = malloc(t.len);
1635 The tail of the string can be 0, 1, or 2 letters
1638 if (i >= 0 && isalpha(t.txt[i-1]))
1640 if (i >= 0 && isalpha(t.txt[i-1]))
1642 strncpy(tail, t.txt+i, t.len-i);
1651 Stripping the quote of a single-line string is trivial.
1652 The only part that is at all interesting is that quote character must
1656 if (t.txt[t.len-1] != quote)
1666 For a multi-line string we have a little more work to do. We need to
1667 remove 3 quotes, not 1, and need to count the indent of the close
1668 quote as it will need to be stripped from all lines.
1672 t.txt[1] != quote || t.txt[2] != quote ||
1673 !is_newline(t.txt[3]))
1678 if (i <= 0 || t.txt[i-1] != quote)
1681 if (i <= 0 || t.txt[i-1] != quote)
1684 if (i <= 0 || t.txt[i-1] != quote)
1688 while (i > 0 && !is_newline(t.txt[i-1]))
1692 if (t.txt[i] == ' ')
1694 if (t.txt[i] == '\t')
1695 indent = indent_tab(indent);
1704 Now we just take one byte at a time. trans-ASCII unicode won't look
1705 like anything we are interested in so it will just be copied byte by
1710 for (i = 0; i < t.len; i++) {
1724 } else if (i+1 >= t.len) {
1725 // escape and end of string
1733 str->len = cp - str->txt;
1741 Every time we find a start of line, we strip spaces and tabs until the
1742 required indent is found.
1745 while (i < t.len && skipped < indent) {
1750 skipped = indent_tab(c);
1759 *cp++ = '\n'; break;
1761 *cp++ = '\r'; break;
1763 *cp++ = '\t'; break;
1765 *cp++ = '\b'; break;
1767 *cp++ = quote; break;
1769 *cp++ = '\f'; break;
1771 *cp++ = '\v'; break;
1773 *cp++ = '\a'; break;
1778 // 3 digit octal number
1781 if (t.txt[i+1] < '0' || t.txt[i+1] > '7' ||
1782 t.txt[i+2] < '0' || t.txt[i+1] > '7')
1784 n = (t.txt[i ]-'0') * 64 +
1785 (t.txt[i+1]-'0') * 8 +
1786 (t.txt[i+2]-'0') * 1;
1792 n = take_hex(2, t.txt+i+1, t.len-i-1);
1800 // 4 or 8 hex digits for unicode
1801 n = take_hex(c == 'u'?4:8, t.txt+i+1, t.len-i-1);
1804 memset(&pstate, 0, sizeof(pstate));
1805 n = wcrtomb(cp, n, &pstate);
1809 i += c == 'u' ? 4 : 8;
1814 else if (is_newline(c))
1824 For `\x` `\u` and `\U` we need to collect a specific number of
1827 ###### string functions
1829 static long take_hex(int digits, char *cp, int l)
1841 else if (isupper(c))
1852 #### File: libstring.c
1854 String parsing goes in `libstring.c`
1863 #include "scanner.h"
1867 ###### File: string.h
1868 int string_parse(struct token *tok, char escape,
1869 struct text *str, char tail[3]);
1871 ###### File: scanner.mk
1873 libstring.o : libstring.c
1874 $(CC) $(CFLAGS) -c libstring.c
1879 As "untested code is buggy code" we need a program to easily test
1880 the scanner library. This will simply parse a given file and report
1881 the tokens one per line.
1883 ###### File: scanner.c
1889 #include <sys/mman.h>
1895 #include "scanner.h"
1900 static void pr_err(char *msg)
1903 fprintf(stderr, "%s\n", msg);
1906 int main(int argc, char *argv[])
1911 struct token_state *state;
1912 const char *known[] = {
1921 struct token_config conf = {
1924 .words_marks = known,
1925 .number_chars = "., _+-",
1926 .known_count = sizeof(known)/sizeof(known[0]),
1927 .ignored = (0 << TK_line_comment)
1928 |(0 << TK_block_comment),
1930 struct section *table, *s, *prev;
1931 setlocale(LC_ALL,"");
1933 fprintf(stderr, "Usage: scanner file\n");
1936 fd = open(argv[1], O_RDONLY);
1938 fprintf(stderr, "scanner: cannot open %s: %s\n",
1939 argv[1], strerror(errno));
1942 len = lseek(fd, 0, 2);
1943 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
1944 table = code_extract(file, file+len, pr_err);
1947 (code_free(s->code), prev = s, s = s->next, free(prev))) {
1948 printf("Tokenizing: %.*s\n", s->section.len,
1950 state = token_open(s->code, &conf);
1952 struct token tk = token_next(state);
1953 printf("%d:%d ", tk.line, tk.col);
1954 token_trace(stdout, tk, 20);
1955 if (tk.num == TK_number) {
1958 if (number_parse(num, tail,tk.txt)) {
1959 printf(" %s ", tail);
1960 mpq_out_str(stdout, 10, num);
1963 printf(" BAD NUMBER");
1965 if (tk.num == TK_string ||
1966 tk.num == TK_multi_string) {
1970 if (tk.txt.txt[0] == '`')
1972 if (string_parse(&tk, esc,
1974 printf(" %s ", tail);
1975 text_dump(stdout, str, 20);
1978 printf(" BAD STRING");
1981 if (tk.num == TK_error)
1983 if (tk.num == TK_eof)
1989 ###### File: scanner.mk
1990 scanner.c : scanner.mdc
1993 scanner : scanner.o scanner.h libscanner.o libmdcode.o mdcode.h
1994 $(CC) $(CFLAGS) -o scanner scanner.o libscanner.o \
1995 libmdcode.o libnumber.o libstring.o -licuuc -lgmp
1996 scanner.o : scanner.c
1997 $(CC) $(CFLAGS) -c scanner.c