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58 lines
1.5 KiB
C
58 lines
1.5 KiB
C
#include "textcode.h"
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#include "haveinline.h"
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static inline int dec(unsigned char x) {
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if (x>='A' && x<='Z') return x-'A';
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if (x>='a' && x<='z') return x-'a'+26;
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if (x>='0' && x<='9') return x-'0'+26+26;
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switch (x) {
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case '+': return 62;
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case '/': return 63;
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default: return -1;
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}
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}
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size_t scan_base64(const char *src,char *dest,size_t *destlen) {
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unsigned short tmp=0,bits=0;
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register const unsigned char* s=(const unsigned char*) src;
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const char* orig=src;
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size_t i,j=0;
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for (i=0;;) {
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int a=dec(*s);
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if (a<0) {
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int equal=(*s=='=');
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while (*s=='=' && ((s-(const unsigned char*)src)&3)) ++s;
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tmp &= ((1<<bits)-1);
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if (!tmp || equal) { j=i; orig=(const char*)s; }
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break;
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}
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tmp=(tmp<<6)|a; bits+=6;
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++s;
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if (bits>=8) {
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bits-=8;
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if (dest) dest[i]=(tmp>>bits);
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++i;
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if (!bits) { j=i; orig=(const char*)s; }
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}
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}
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if (destlen) *destlen=j;
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return orig-src;
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}
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#ifdef UNITTEST
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#include <assert.h>
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#include <string.h>
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#include <stdio.h>
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int main() {
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char buf[100];
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size_t l;
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memset(buf,0,10); assert(scan_base64("Zm5vcmQ=",buf,&l)==8 && l==5 && !memcmp(buf,"fnord",6));
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/* check that we don't insist on the padding */
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memset(buf,0,10); assert(scan_base64("Zm5vcmQ",buf,&l)==7 && l==5 && !memcmp(buf,"fnord",6));
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/* check the special non-isalnum chars :) */
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memset(buf,0,10); assert(scan_base64("/+8=",buf,&l)==4 && l==2 && !memcmp(buf,"\xff\xef",3));
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return 0;
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}
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#endif
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