Ragel is a State Machine Compiler that supports generating code from Ragel’s regular expressions. Ragel provides code generation for C, C++, Objective-C, D, Java, and Ruby. Regular expressions and finite automata can be used in protocol analysis, data parsing, lexical analysis, and input validation. Implementing Ragel’s C code is very easy. Here is an atoi implementation for C’s standard library. It is several times faster than C standard library’s implementation.
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/* * Convert a string to an integer. */ #include <stdlib.h> #include <string.h> #include <stdio.h> %%{ machine atoi; write data; }%% long long atoi( char *str ) { char *p = str, *pe = str + strlen( str ); int cs; long long val = 0; bool neg = false; %%{ action see_neg { neg = true; } action add_digit { val = val * 10 + (fc - '0'); } main := ( '-'@see_neg | '+' )? ( digit @add_digit )+ 'n'; # Initialize and execute. write init; write exec; }%% if ( neg ) val = -1 * val; if ( cs < atoi_first_final ) fprintf( stderr, "atoi: there was an errorn" ); return val; }; #define BUFSIZE 1024 int main() { char buf[BUFSIZE]; while ( fgets( buf, sizeof(buf), stdin ) != 0 ) { long long value = atoi( buf ); printf( "%lldn", value ); } return 0; } |