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);
373 if (ignored & (1<<TK_mark))
382 Strings start with one of single quote, double quote, or back quote
383 and continue until a matching character on the same line. Any of
384 these characters can be included in the list of known marks and then
385 they will not be used for identifying strings.
387 Immediately following the close quote one or two ASCII letters may
388 appear. These are somewhat like the arbitrary letters allowed in
389 "Numbers" above. They can be used by the language in various ways.
391 If 3 identical quote characters appear in a row and are
392 followed by a newline, then this forms a multi-line string which
393 continues until an identical triple quote appears on a line preceded
394 only by whitespace and followed immediately by 0-2 ASCII letters and a newline.
396 Multi-line strings may not extend beyond the end of the `code_node` in
399 Normal strings and multi-line strings are encoded as two different
406 ###### internal functions
407 static int is_quote(wchar_t ch)
409 return ch == '\'' || ch == '"' || ch == '`';
412 #### Multi-line strings
414 The multi-line string is checked for first. If they are being
415 ignored, we fall through and treat a triple quote as an empty string
416 followed by the start of a new string.
419 if (tk.txt.len == 3 &&
420 !(ignored & (1 << TK_multi_string)) &&
421 is_quote(tk.txt.txt[0]) &&
422 memcmp(tk.txt.txt, tk.txt.txt+1, 2) == 0 &&
423 is_newline(tk.txt.txt[3])) {
425 wchar_t first = tk.txt.txt[0];
428 while (!at_eon(state) && qseen < 3) {
429 ch = get_char(state);
430 if (is_newline(ch)) {
433 } else if (at_sol && ch == first) {
435 } else if (ch != ' ' && ch != '\t') {
441 /* Hit end of node - error.
442 * unget so the newline is seen,
443 * but return rest of string as an error.
446 close_token(state, &tk);
450 /* 2 letters are allowed */
451 ch = get_char(state);
453 ch = get_char(state);
455 ch = get_char(state);
456 /* Now we must have a newline, but we don't return it
459 close_token(state, &tk);
460 tk.num = TK_multi_string;
466 #### Single-line strings
468 The sequence of marks collected may be more than a single-line
469 string, so we reset to the start and collect characters until
470 we find a close quote or a newline.
472 If `TK_string` is ignored, then quote characters will appear as `TK_mark`s.
475 if (tk.txt.len && is_quote(tk.txt.txt[0]) &&
476 !(ignored & (1<<TK_string))) {
477 wchar_t first = tk.txt.txt[0];
478 reset_token(state, &tk);
481 ch = get_char(state);
482 while (ch != first && !is_newline(ch));
484 if (is_newline(ch)) {
488 close_token(state, &tk);
494 Single line comments may start with '`//`' or '`#`' providing that these
495 are not known marks. They continue to the end of the line.
497 Block comments start with '`/*`' if this is not a known mark. They
498 continue to the first occurrence of '`*/`' and may not contain any
499 occurrence of '`/*`'.
501 Block comments can be wholly within one line or can continue over
502 multiple lines. The multi-line version should be followed immediately
503 by a newline. The Linux kernel contains over 285000 multi-line
504 comments are only 34 are followed by characters other than white space
505 (which should be removed) or a backslash (only needed in macros). So
506 it would not suffer from this rule.
508 These two comment types are reported as two separate token types, and
509 consequently can be ignored separately. When ignored a comment is
510 still parsed, but is discarded.
516 ###### internal functions
517 static int is_line_comment(struct text txt)
519 return (txt.len >= 1 && txt.txt[0] == '#') ||
520 (txt.len >= 2 && txt.txt[0] == '/' &&
524 static int is_block_comment(struct text txt)
526 return txt.len >= 2 && txt.txt[0] == '/' &&
530 #### Single line comments
532 A single-line comment continues up to, but not including the newline.
536 if (is_line_comment(tk.txt)) {
537 while (!is_newline(ch))
538 ch = get_char(state);
540 close_token(state, &tk);
541 tk.num = TK_line_comment;
542 if (ignored & (1 << TK_line_comment))
549 The token text collected so far could exceed the comment, so we need
552 If we find an embedded `/*` we reset to just before the '/' and report
553 an error. That way the next thing to be parsed will be the rest of
554 the comment. This requires a double unget, so we need to save/restore
555 the unget state (explained later).
559 if (is_block_comment(tk.txt)) {
562 reset_token(state, &tk);
565 save_unget_state(state);
566 ch = get_char(state);
568 while (!at_eon(state) &&
569 (prev != '/' || ch != '*') &&
570 (prev != '*' || ch != '/')) {
574 save_unget_state(state);
575 ch = get_char(state);
577 close_token(state, &tk);
583 /* embedded. Need to unget twice! */
584 restore_unget_state(state);
589 tk.num = TK_block_comment;
590 if (newlines && !(ignored & (1<<TK_newline))) {
591 /* next char must be newline */
592 ch = get_char(state);
597 if (tk.num == TK_error ||
598 !(ignored & (1 << TK_block_comment)))
603 ### Indents, Newlines, and White Space.
605 Normally white space is ignored. However newlines can be important as
606 can indents, which are either after a newline or at the start of a
607 node (detected by `at_son()`);
609 ###### exported functions
610 static inline int is_newline(wchar_t ch)
612 return ch == '\n' || ch == '\f' || ch == '\v';
616 if (ch <= ' ' && !is_newline(ch)
620 If a line starts with more white-space than the previous non-blank
621 line - or if the first non-blank line in the document starts with any
622 white-space - then an "IN" is reported at the start of the line.
624 Before the next non-blank line which starts with less white space, or
625 at the latest at the end of the document, a matching "OUT" token
626 is reported. There will always be an exact match between "IN" and
629 It is possible for "OUT" to be followed (almost) immediately by an
630 "IN". This happens if, for example, the indent of three consecutive
631 lines are 0, 8, 4 spaces. Before the second line we report an
632 "IN". Before the third line we must report an "OUT", as 4 is less
633 than 8, then also an Ident as 4 is greater than 0.
639 For the purpose of measuring the length of white space, a tab adds at
640 least one space, and rounds up to a multiple of 8.
642 ###### exported functions
643 static inline int indent_tab(int indent)
648 We need to track the current levels of indent. This requires some
649 sort of stack as indent levels are pushed on and popped off. In
650 practice this stack is unlikely to often exceed 5 so we will used a
651 fixed stack of 20 indent levels. More than this will be silently
656 int indent_sizes[20];
660 Newlines can optionally be reported. Newlines within a block comment
661 or a multi-line string are not reported separately, but each of these
662 must be followed immediately by a newline so these constructs cannot
663 hide the fact that a newline was present.
665 When indents are being reported, the Newline which would normally be
666 reported immediately before the "IN" is delayed until after the
667 matching "OUT". This makes an indented section act like a
668 continuation of the previous line to some extent.
670 A blank line would normally be reported simply as two consecutive Newline
671 tokens. However if the subsequent line is indented (and indents are being
672 reported) then the right thing to do is less obvious as Newlines should be
673 delayed - but how many Newlines?
675 The approach we will take is to report the extra Newlines immediately after
676 the IN token, so the blank line is treated as though it were an indented
682 If we find a newline or white space at the start of a block, we keep
683 collecting spaces, tabs, and newlines until we find some real text.
684 Then depending on the indent we generate some number of tokens. These
685 will be a sequence of "Newline OUT" pairs representing a decrease
686 in indent, then either a Newline or an IN depending on whether the
687 next line is indented, then zero or more Newlines representing all the
688 blank lines that have been skipped.
690 When a Newline leads to the next block of code there is a question of
691 whether the various Newline and OUT/IN tokens should appear to
692 pbelong to the earlier or later block. This is addressed by processing
693 the tokens in two stages based on the relative indent levels of the
694 two blocks (each block has a base indent to which the actual indents
697 Any "Newline OUT" pairs needed to reduce the current indent to the
698 maximum of the base indents of the old and new blocks are generated
699 against the old block. Then if the next block does not have an
700 increased indent, one more "Newline" is generated.
702 If further "Newline OUT" pairs are needed to get to the indent
703 level of the 'next' block, they are generated against that block,
704 though the first Newline is suppressed (it having already been
707 Finally the Newline or IN for the first line of the new block is
708 generated, unless the Newline needs to be suppressed because it
709 appeared at the end of the previous block.
711 This means that a block may start with an OUT or an IN, but
712 will only start with a Newline if it actually starts with a blank
715 We will need to represent in the `token_state` where in this sequence
716 of delayed tokens we are. As `state.col` records the target indent we
717 don't need to record how many OUTs or INs are needed. We do
718 need to record the number of blank lines, and which of Newline and
719 OUT is needed next in the initial sequence of pairs.
721 For this we store one more than the number of blank lines as
722 `delayed_lines` and a flag for `out_next`.
729 Generating these tokens involve two separate pieces of code.
731 Firstly we need to recognise white space and count the indents and
732 newlines. These are recorded in the above state fields.
734 Separately we need, on each call to `token_next`, we need to check if
735 there are some delayed tokens and if so we need to advance the state
736 information and return one token.
739 if (is_newline(ch) || (at_son(state) && ch <= ' ')) {
741 int was_son = at_son(state);
742 if (ignored & (1<<TK_in)) {
745 if (ignored & (1<<TK_newline))
748 close_token(state, &tk);
751 // Indents are needed, so check all white space.
752 while (ch <= ' ' && !at_eon(state)) {
755 ch = get_char(state);
759 if (state->node->next &&
760 state->node->next->indent > state->node->indent)
761 state->col = state->node->next->indent;
763 state->col = state->node->indent;
766 state->delayed_lines = newlines;
767 state->out_next = was_son;
768 state->check_indent = 1;
773 ###### delayed tokens
775 if (state->check_indent || state->delayed_lines) {
776 if (state->col < state->indent_sizes[state->indent_level]) {
777 if (!state->out_next &&
778 !(ignored & (1<<TK_newline))) {
783 state->indent_level -= 1;
788 if (state->col > state->indent_sizes[state->indent_level] &&
789 state->indent_level < sizeof(state->indent_sizes)-1) {
790 state->indent_level += 1;
791 state->indent_sizes[state->indent_level] = state->col;
792 state->delayed_lines -= 1;
796 state->check_indent = 0;
797 if (state->delayed_lines && !(ignored & (1<<TK_newline))) {
799 state->delayed_lines -= 1;
802 state->delayed_lines = 0;
808 After the last newline in the file has been processed, a special
809 end-of-file token will be returned. any further attempts to get more
810 tokens will continue to return the same end-of-file token.
822 ### Unknown Marks, or errors.
824 We have now handled all the possible known mark-like tokens.
825 If the token we have is not empty and `TK_mark` is allowed,
826 we have an unknown mark, otherwise this must be an error.
829 /* one unknown character */
830 close_token(state, &tk);
834 ## Tools For The Task
836 You may have noticed that are few gaps we left in the above -
837 functions used without first defining them. Doing so above would have
840 ### Character by character
842 As we walk through the various `code_node`s we need to process whole
843 Unicode codepoints, and keep track of which line and column we are on.
844 We will assume for now that any printing character uses one column,
845 though that is not true in general.
847 As the text in a `code_node` may include an indent that identifies it as
848 being code, we need to be careful to strip that. The `code_node` has
849 a flag that tells us whether or not we need to strip.
855 struct code_node *node;
860 ###### internal functions
862 static void do_strip(struct token_state *state)
864 if (state->node->needs_strip) {
866 while (n && state->node->code.txt[state->offset] == ' ') {
870 while (n == 4 && state->node->code.txt[state->offset] == '\t') {
877 static wint_t get_char(struct token_state *state)
883 if (state->node == NULL)
885 if (state->node->code.len <= state->offset) {
887 state->node = state->node->next;
888 while (state->node && state->node->code.txt == NULL);
890 if (state->node == NULL)
893 state->line = state->node->line_no;
894 state->col = state->node->indent;
899 memset(&mbstate, 0, sizeof(mbstate));
901 n = mbrtowc(&next, state->node->code.txt + state->offset,
902 state->node->code.len - state->offset,
904 if (n == -2 || n == 0) {
905 /* Not enough bytes - not really possible */
907 state->offset = state->node->code.len;
908 } else if (n == -1) {
911 next = 0x7f; // an illegal character
917 } else if (is_newline(next)) {
919 state->col = state->node->indent;
921 } else if (next == '\t') {
922 state->col = indent_tab(state->col);
927 We will sometimes want to "unget" the last character as it needs to be
928 considered again as part of the next token. So we need to store a
929 'previous' version of all metadata.
936 ###### before get_char
937 state->prev_offset = state->offset;
938 state->prev_line = state->line;
939 state->prev_col = state->col;
941 ###### internal functions
943 static void unget_char(struct token_state *state)
946 state->offset = state->prev_offset;
947 state->line = state->prev_line;
948 state->col = state->prev_col;
952 We occasionally need a double-unget, particularly for numbers and
953 block comments. We don't impose this cost on all scanning, but
954 require those code sections that need it to call `save_unget_state`
955 before each `get_char`, and then `restore_unget_state` when a
956 double-unget is needed.
963 ###### internal functions
964 static void save_unget_state(struct token_state *state)
966 state->prev_offset2 = state->prev_offset;
967 state->prev_line2 = state->prev_line;
968 state->prev_col2 = state->prev_col;
971 static void restore_unget_state(struct token_state *state)
973 state->prev_offset = state->prev_offset2;
974 state->prev_line = state->prev_line2;
975 state->prev_col = state->prev_col2;
978 At the start of a token we don't want to be at the end of a code block
979 if we can help it. To avoid this possibility, we 'get' and 'unget' a
980 single character. This will move into the next non-empty code block
981 and leave the current pointer at the start of it.
983 This has to happen _after_ dealing with delayed tokens as some of them
984 must appear in the previous node. When we do this, we need to reset
985 the data in the token.
987 ###### delayed tokens
991 tk.node = state->node;
993 tk.txt.txt = state->node->code.txt + state->offset;
994 tk.line = state->line;
1001 The current token is initialized to line up with the first character
1002 that we 'get' for each token. When we have, or might have, a full
1003 token we can call `close_token` to set the `len` of the token
1004 appropriately. This can safely be called multiple times.
1006 Finally we occasionally (for single-line strings and block comments)
1007 need to reset to the beginning of the current token as we might have
1008 parsed too much already. For that there is `reset_token`.
1011 tk.node = state->node;
1013 tk.txt.txt = state->node->code.txt + state->offset;
1014 tk.line = state->line;
1015 tk.col = state->col;
1018 ###### internal functions
1020 static void close_token(struct token_state *state,
1023 tk->txt.len = (state->node->code.txt + state->offset)
1027 static void reset_token(struct token_state *state, struct token *tok)
1029 state->prev_line = tok->line;
1030 state->prev_col = tok->col;
1031 state->prev_offset = tok->txt.txt - state->node->code.txt;
1037 Tokens make not cross into the next `code_node`, and some tokens can
1038 include the newline at the and of a `code_node`, we must be able to
1039 easily check if we have reached the end. Equally we need to know if
1040 we are at the start of a node, as white space is treated a little
1043 ###### internal functions
1045 static int at_son(struct token_state *state)
1047 return state->offset == 0;
1050 static int at_eon(struct token_state *state)
1052 // at end-of-node ??
1053 return state->node == NULL ||
1054 state->offset >= state->node->code.len;
1057 ### Find a known word
1059 As the known-word list is sorted we can use a simple binary search.
1060 Following the pattern established in "mdcode", we will use a `struct
1061 text` with start and length to represent the code fragment we are
1064 ###### internal functions
1065 static int find_known(struct token_config *conf, struct text txt)
1068 int hi = conf->known_count;
1070 while (lo + 1 < hi) {
1071 int mid = (lo + hi) / 2;
1072 int cmp = strncmp(conf->words_marks[mid],
1074 if (cmp == 0 && conf->words_marks[mid][txt.len])
1081 if (strncmp(conf->words_marks[lo],
1082 txt.txt, txt.len) == 0
1083 && conf->words_marks[lo][txt.len] == 0)
1089 ### Bringing it all together
1091 Now we have all the bits there is just one section missing: combining
1092 all the token parsing code into one block.
1094 The handling of delayed tokens (Newlines, INs, OUTs) must come
1095 first before we try getting another character.
1097 Then we parse all the test, making sure that we check for known marks
1098 before strings and comments, but unknown marks after strings and comments.
1100 This block of code will either return a token, or will choose to
1101 ignore one, in which case it will `continue` around to the top of the
1107 ch = get_char(state);
1119 As well as getting tokens, we need to be able to create the
1120 `token_state` to start with, and discard it later.
1125 ###### main functions
1126 struct token_state *token_open(struct code_node *code, struct
1129 struct token_state *state = malloc(sizeof(*state));
1130 memset(state, 0, sizeof(*state));
1132 state->line = code->line_no;
1133 state->col = code->indent;
1138 void token_close(struct token_state *state)
1143 ###### exported functions
1144 struct token_state *token_open(struct code_node *code, struct
1145 token_config *conf);
1146 void token_close(struct token_state *state);
1150 Getting tokens is the main thing but it is also useful to be able to
1151 print out token information, particularly for tracing and testing.
1153 Known tokens are printed verbatim. Other tokens are printed as
1154 `type(content)` where content is truncated to a given number of characters.
1156 The function for printing a truncated string (`text_dump`) is also exported
1157 so that it can be used to tracing processed strings too.
1162 ###### exported functions
1163 void token_trace(FILE *f, struct token tok, int max);
1164 void text_dump(FILE *f, struct text t, int max);
1166 ###### main functions
1168 void text_dump(FILE *f, struct text txt, int max)
1175 for (i = 0; i < max; i++) {
1176 char c = txt.txt[i];
1177 if (c < ' ' || c > '~')
1178 fprintf(f, "\\x%02x", c & 0xff);
1182 fprintf(f, "%c", c);
1188 void token_trace(FILE *f, struct token tok, int max)
1190 static char *types[] = {
1191 [TK_ident] = "ident",
1193 [TK_number] = "number",
1194 [TK_string] = "string",
1195 [TK_multi_string] = "mstring",
1196 [TK_line_comment] = "lcomment",
1197 [TK_block_comment] = "bcomment",
1200 [TK_newline] = "newline",
1202 [TK_error] = "ERROR",
1206 default: /* known word or mark */
1207 fprintf(f, "%.*s", tok.txt.len, tok.txt.txt);
1213 /* No token text included */
1214 fprintf(f, "%s()", types[tok.num]);
1220 case TK_multi_string:
1221 case TK_line_comment:
1222 case TK_block_comment:
1224 fprintf(f, "%s(", types[tok.num]);
1225 text_dump(f, tok.txt, max);
1231 ### And there we have it
1233 We now have all the library functions defined for reading and printing
1234 tokens. Now we just need C files to store them, and a mk file to make them.
1236 ###### File: scanner.h
1238 ## exported functions
1240 ###### File: libscanner.c
1242 #include "scanner.h"
1244 ## internal functions
1247 ###### File: scanner.mk
1251 scanner.mk scanner.h libscanner.c : scanner.mdc
1254 libscanner.o : libscanner.c
1255 $(CC) $(CFLAGS) -c libscanner.c
1257 ## Processing numbers
1259 Converting a `TK_number` token to a numerical value is a slightly
1260 higher level task than lexical analysis, and slightly lower than
1261 grammar parsing, so put it here - as an index if you like.
1263 Importantly it will be used by the same testing rig that is used for
1264 testing the token scanner.
1266 The numeric value that we will convert all numbers into is the `mpq_t`
1267 from the GNU high precision number library "libgmp".
1269 ###### number includes
1273 Firstly we need to be able to parse a string of digits in a given base
1274 and possibly with a decimal marker. We store this in an `mpz_t`
1275 integer and report the number of digits after the decimal mark.
1277 On error we return zero and ensure that the 'mpz_t' has been freed, or
1278 had never been initialised.
1280 ###### number functions
1282 static int parse_digits(mpz_t num, struct text tok, int base,
1285 /* Accept digits up to 'base', ignore '_' and
1286 * ' ' if they appear between two legal digits,
1287 * and if `placesp` is not NULL, allow a single
1288 * '.' or ',' and report the number of digits
1290 * Return number of characters processed (p),
1291 * or 0 if something illegal was found.
1294 int decimal = -1; // digits after marker
1295 enum {Digit, Space, Other} prev = Other;
1298 for (p = 0; p < tok.len; p++) {
1300 char c = tok.txt[p];
1302 if (c == '_' || c == ' ') {
1308 if (c == '.' || c == ',') {
1311 if (!placesp || decimal >= 0)
1319 else if (isupper(c))
1321 else if (islower(c))
1332 mpz_mul_ui(num, num, base);
1336 mpz_add_ui(num, num, dig);
1355 ###### number includes
1358 To parse a full number we need to consider the optional base, the
1359 mantissa, and the optional exponent. We will treat these one at a
1362 The base is indicated by a letter after a leading zero, which must be
1363 followed by a base letter or a period. The base also determines the
1364 character which will mark an exponent.
1372 if (tok.txt[0] == '0' && tok.len > 1) {
1374 switch(tok.txt[1]) {
1405 // another digit is not permitted
1409 // must be decimal marker or trailing
1410 // letter, which are OK;
1417 After the base is the mantissa, which may contain a decimal mark, so
1418 we need to record the number of places. We won't impose the number of
1419 places until we have the exponent as well.
1426 ###### parse mantissa
1428 d = parse_digits(mant, tok, base, &places);
1434 mpq_set_z(num, mant);
1437 After the mantissa number may come an exponent which may be positive
1438 or negative. We assume at this point that we have seen the exponent
1446 ###### parse exponent
1448 if (tok.txt[0] == '+') {
1451 } else if (tok.txt[0] == '-') {
1457 d = parse_digits(exp, tok, 10, NULL);
1462 if (!mpz_fits_slong_p(exp)) {
1467 lexp = mpz_get_si(exp) * esign;
1473 Now that we have the mantissa and the exponent we can multiply them
1474 together, also allowing for the number of digits after the decimal
1477 For base 10, we simply subtract the decimal places from the exponent.
1478 For the other bases, as the exponent is alway based on 2, even for
1479 octal and hex, we need a bit more detail.
1480 We then recover the sign from the exponent, as division is quite
1481 different from multiplication.
1483 ###### calc exponent
1502 Imposing the exponent on the number is also very different for base 10
1503 than for the others. For the binary shift `gmp` provides a simple
1504 function. For base 10 we use something like Russian Peasant
1507 ###### calc exponent
1511 mpq_set_ui(tens, 10, 1);
1515 mpq_mul(num, num, tens);
1517 mpq_div(num, num, tens);
1522 mpq_mul(tens, tens, tens);
1527 mpq_mul_2exp(num, num, lexp);
1529 mpq_div_2exp(num, num, lexp);
1532 Now we are ready to parse a number: the base, mantissa, and exponent.
1533 If all goes well we check for the possible trailing letters and
1534 return. Return value is 1 for success and 0 for failure.
1537 ###### number functions
1538 int number_parse(mpq_t num, char tail[3], struct text tok)
1545 if (tok.len > 1 && (tok.txt[0] == expc ||
1546 tok.txt[0] == toupper(expc))) {
1553 for (i = 0; i < 2; i++) {
1556 if (!isalpha(tok.txt[i]))
1558 tail[i] = tok.txt[i];
1568 Number parsing goes in `libnumber.c`
1570 ###### File: libnumber.c
1578 ###### File: number.h
1579 int number_parse(mpq_t num, char tail[3], struct text tok);
1581 ###### File: scanner.mk
1583 libnumber.o : libnumber.c
1584 $(CC) $(CFLAGS) -c libnumber.c
1586 ## Processing strings
1588 Both `TK_string` and `TK_multi_string` require post-processing which
1589 can be one of two types: literal or with escapes processed.
1590 Even literal processing is non-trivial as the file may contain indents
1591 which need to be stripped.
1593 Errors can only occur when processing escapes. Any unrecognised
1594 character following the escape character will cause an error.
1596 Processing escapes and striping indents can only make the string
1597 shorter, not longer, so we allocate a buffer which is the same size as
1598 the string and process into that.
1600 To request escape processing, we pass the character we want to use for
1601 quoting, usually '`\`'. To avoid escape processing we pass a zero.
1604 int string_parse(struct token *tok, char escape,
1605 struct text *str, char tail[3])
1608 struct text t = tok->txt;
1612 if (tok->num == TK_string) {
1617 str->txt = malloc(t.len);
1630 The tail of the string can be 0, 1, or 2 letters
1633 if (i >= 0 && isalpha(t.txt[i-1]))
1635 if (i >= 0 && isalpha(t.txt[i-1]))
1637 strncpy(tail, t.txt+i, t.len-i);
1646 Stripping the quote of a single-line string is trivial.
1647 The only part that is at all interesting is that quote character must
1651 if (t.txt[t.len-1] != quote)
1661 For a multi-line string we have a little more work to do. We need to
1662 remove 3 quotes, not 1, and need to count the indent of the close
1663 quote as it will need to be stripped from all lines.
1667 t.txt[1] != quote || t.txt[2] != quote ||
1668 !is_newline(t.txt[3]))
1673 if (i <= 0 || t.txt[i-1] != quote)
1676 if (i <= 0 || t.txt[i-1] != quote)
1679 if (i <= 0 || t.txt[i-1] != quote)
1683 while (i > 0 && !is_newline(t.txt[i-1]))
1687 if (t.txt[i] == ' ')
1689 if (t.txt[i] == '\t')
1690 indent = indent_tab(indent);
1699 Now we just take one byte at a time. trans-ASCII unicode won't look
1700 like anything we are interested in so it will just be copied byte by
1705 for (i = 0; i < t.len; i++) {
1719 } else if (i+1 >= t.len) {
1720 // escape and end of string
1728 str->len = cp - str->txt;
1736 Every time we find a start of line, we strip spaces and tabs until the
1737 required indent is found.
1740 while (i < t.len && skipped < indent) {
1745 skipped = indent_tab(c);
1754 *cp++ = '\n'; break;
1756 *cp++ = '\r'; break;
1758 *cp++ = '\t'; break;
1760 *cp++ = '\b'; break;
1762 *cp++ = quote; break;
1764 *cp++ = '\f'; break;
1766 *cp++ = '\v'; break;
1768 *cp++ = '\a'; break;
1773 // 3 digit octal number
1776 if (t.txt[i+1] < '0' || t.txt[i+1] > '7' ||
1777 t.txt[i+2] < '0' || t.txt[i+1] > '7')
1779 n = (t.txt[i ]-'0') * 64 +
1780 (t.txt[i+1]-'0') * 8 +
1781 (t.txt[i+2]-'0') * 1;
1787 n = take_hex(2, t.txt+i+1, t.len-i-1);
1795 // 4 or 8 hex digits for unicode
1796 n = take_hex(c == 'u'?4:8, t.txt+i+1, t.len-i-1);
1799 memset(&pstate, 0, sizeof(pstate));
1800 n = wcrtomb(cp, n, &pstate);
1804 i += c == 'u' ? 4 : 8;
1809 else if (is_newline(c))
1819 For `\x` `\u` and `\U` we need to collect a specific number of
1822 ###### string functions
1824 static long take_hex(int digits, char *cp, int l)
1836 else if (isupper(c))
1847 #### File: libstring.c
1849 String parsing goes in `libstring.c`
1858 #include "scanner.h"
1862 ###### File: string.h
1863 int string_parse(struct token *tok, char escape,
1864 struct text *str, char tail[3]);
1866 ###### File: scanner.mk
1868 libstring.o : libstring.c
1869 $(CC) $(CFLAGS) -c libstring.c
1874 As "untested code is buggy code" we need a program to easily test
1875 the scanner library. This will simply parse a given file and report
1876 the tokens one per line.
1878 ###### File: scanner.c
1884 #include <sys/mman.h>
1890 #include "scanner.h"
1895 static void pr_err(char *msg)
1898 fprintf(stderr, "%s\n", msg);
1901 int main(int argc, char *argv[])
1906 struct token_state *state;
1907 const char *known[] = {
1916 struct token_config conf = {
1919 .words_marks = known,
1920 .number_chars = "., _+-",
1921 .known_count = sizeof(known)/sizeof(known[0]),
1922 .ignored = (0 << TK_line_comment)
1923 |(0 << TK_block_comment),
1925 struct section *table, *s, *prev;
1926 setlocale(LC_ALL,"");
1928 fprintf(stderr, "Usage: scanner file\n");
1931 fd = open(argv[1], O_RDONLY);
1933 fprintf(stderr, "scanner: cannot open %s: %s\n",
1934 argv[1], strerror(errno));
1937 len = lseek(fd, 0, 2);
1938 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
1939 table = code_extract(file, file+len, pr_err);
1942 (code_free(s->code), prev = s, s = s->next, free(prev))) {
1943 printf("Tokenizing: %.*s\n", s->section.len,
1945 state = token_open(s->code, &conf);
1947 struct token tk = token_next(state);
1948 printf("%d:%d ", tk.line, tk.col);
1949 token_trace(stdout, tk, 20);
1950 if (tk.num == TK_number) {
1953 if (number_parse(num, tail,tk.txt)) {
1954 printf(" %s ", tail);
1955 mpq_out_str(stdout, 10, num);
1958 printf(" BAD NUMBER");
1960 if (tk.num == TK_string ||
1961 tk.num == TK_multi_string) {
1965 if (tk.txt.txt[0] == '`')
1967 if (string_parse(&tk, esc,
1969 printf(" %s ", tail);
1970 text_dump(stdout, str, 20);
1973 printf(" BAD STRING");
1976 if (tk.num == TK_error)
1978 if (tk.num == TK_eof)
1984 ###### File: scanner.mk
1985 scanner.c : scanner.mdc
1988 scanner : scanner.o scanner.h libscanner.o libmdcode.o mdcode.h
1989 $(CC) $(CFLAGS) -o scanner scanner.o libscanner.o \
1990 libmdcode.o libnumber.o libstring.o -licuuc -lgmp
1991 scanner.o : scanner.c
1992 $(CC) $(CFLAGS) -c scanner.c