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67 lines
2.7 KiB
67 lines
2.7 KiB
SLRE: Super Light Regular Expression library
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============================================
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SLRE is an ISO C library that implements a subset of Perl regular
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expression syntax. Main focus of SLRE is small size, [simple
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API](https://github.com/cesanta/slre/blob/master/slre.h), clarity of code
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and extensibility. It is making it perfect for tasks like parsing network
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requests, configuration files, user input, etc, when libraries like
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[PCRE](http://pcre.org) are too heavyweight for the given task. Developers in
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embedded would benefit most.
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Extensibility is another great aspect of SLRE. For example, if one wants to
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introduce a new metacharacter, '\i', meaning 'IPv4 address', it is easy to do
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so with SLRE.
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## Supported Syntax
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^ Match beginning of a buffer
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$ Match end of a buffer
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() Grouping and substring capturing
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[...] Match any character from set
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[^...] Match any character but ones from set
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\s Match whitespace
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\S Match non-whitespace
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\d Match decimal digit
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+ Match one or more times (greedy)
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+? Match one or more times (non-greedy)
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* Match zero or more times (greedy)
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*? Match zero or more times (non-greedy)
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? Match zero or once
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\xDD Match byte with hex value 0xDD
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\meta Match one of the meta character: ^$().[*+\?
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x|y Match x or y (alternation operator)
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## API
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int slre_match(const char *regexp, const char *buf, int buf_len,
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struct slre_cap *caps, const char **error_msg);
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`slre_match()` matches string buffer `buf` of length `buf_len` against
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regular expression `regexp`, which should conform the syntax outlined
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above. If regular expression `regexp` contains brackets, `slre_match()`
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will capture the respective substrings. Array of captures, `caps`,
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must have at least as many elements as number of bracket pairs in the `regexp`.
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`slre_match()` returns 0 if there is no match found. Otherwise, it returns
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the number scanned bytes from the beginning of the string. This way,
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it is easy to do repetitive matches. Hint: if it is required to know
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the exact matched substring, enclose `regexp` in a brackets and specify `caps`,
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which should be an array of following structures:
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struct slre_cap {
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const char *ptr; /* Points to the matched fragment */
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int len; /* Length of the matched fragment */
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};
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## Example: parsing HTTP request
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const char *error_msg, *request = " GET /index.html HTTP/1.0\r\n\r\n";
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struct slre_cap caps[4];
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if (slre_match("^\\s*(\\S+)\\s+(\\S+)\\s+HTTP/(\\d)\\.(\\d)",
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request, strlen(request), caps, &error_msg)) {
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} else {
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printf("Error parsing [%s]: [%s]\n", request, error_msg);
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}
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