www.pudn.com > CRGAB.zip > INSTR.C

/* 
HEADER:         ; 
TITLE:          BASIC instr() (in string) function 
VERSION:        1.4; 
 
DESCRIPTION:    performs BASIC instr() function with similar syntax. This 
                comes in handy when manually converting BASIC to C 
 
       syntax: instr(starting_position,string_to_look_in,string_to_find) 
                starting position is 0 to length of line - 1, 
                this function returns 0 to length of line if string was 
                located, or < -1 if not found 
 
KEYWORDS:       ; 
SYSTEM:         Xenix 3.4b, MSDOS; 
FILENAME:       instr.c 
WARNINGS:       compile with -dNO_PROTOTYPE if your system does not 
                support prototyping, with -dFOR_MSDOS if you are compiling 
                for MSDOS with an ANSI standard compiler. 
                Defaults assume compiling with prototypes for 
                Xenix 3.4b on Altos 2086 computer. 
 
SEE-ALSO:       ; 
AUTHORS:        Vern Martin, 449 W. Harrison, Alliance, Ohio 44601; 
COMPILERS:      ECOSOFT ECO-C88, XENIX 3.4B STANDARD COMPILER; 
*/ 
 
#include "vernmath.h" 
#define NOT_FOUND   -1 
 
int instr(position,search,find) 
int position; 
char *search,*find; 
{ 
    int insearch,infind=0,match=0,prefind=0; 
    insearch = position; 
/*  check for error condition   */ 
    if (position > (strlen(search)-1)) { 
        return(NOT_FOUND); 
    } 
    while(search[insearch] != (char) NULL && 
        find[infind] != (char) NULL && match == 0) { 
        if (search[insearch] != find[infind]) { 
            insearch++; 
            continue; 
        } 
/*  record the position of the match of the first char  */ 
        position = insearch++; 
/*  set preliminary find flag to true, preliminary match found */ 
        prefind = 1; 
        infind++; 
        while(search[insearch] != (char) NULL && 
            find[infind] != (char) NULL && match == 0) { 
            if (search[insearch] != find[infind])  { 
/*  do not increment insearch -- it might match the first char of infind */ 
                infind = 0; 
                break; 
            } 
            insearch++; 
            infind++; 
        } 
/*  if you made it to the end of the find string then you have a match */ 
        if (!find[infind]) match = 1; 
/*  if the preliminary find flag is set and a full match has not yet 
    been found then set the search posision to one past fist char match */ 
        if (prefind && !match) { 
            prefind = 0; 
            insearch = position+1; 
        } 
    } 
    if (match) return(position); 
    else return(NOT_FOUND); 
}