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55 lines
1.4 KiB
C
55 lines
1.4 KiB
C
#include "fmt.h"
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#include "textcode.h"
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#include "scan.h"
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size_t scan_jsonescape(const char *src,char *dest,size_t *destlen) {
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register const unsigned char* s=(const unsigned char*) src;
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size_t written=0,i;
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char c;
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unsigned int prev,cur,todo;
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prev=cur=(unsigned int)-1;
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for (i=0; s[i]; ++i) {
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if ((c=s[i])=='\\') {
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switch (s[i+1]) {
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case '\\':
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if (prev!=(unsigned int)-1) return 0; // lead surrogate not followed by tail surrogate
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// c='\\'; // c already is backslash
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break;
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case 'u':
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{
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size_t j;
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for (cur=j=0; j<4; ++j) {
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char x=scan_fromhex(s[i+2+j]);
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if (x<0) return 0; // not hex -> invalid input
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cur=(cur<<4) | x;
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}
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if (cur>=0xd800 && cur<=0xdbff) {
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// utf-16 surrogate pair; needs to be followed by another
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// surrogate. We need to read both and convert to UTF-8
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if (prev!=(unsigned int)-1) return 0; // two lead surrogates
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prev=cur;
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i+=5; // we want i to go up by 6, 1 is done by the for loop
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continue; // write nothing!
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} else if (cur>=0xdc00 && cur<=0xdfff) {
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todo=(cur&0x3ff) | ((prev&0x3ff) << 10) | 0x100000;
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} else
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todo=cur;
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written+=fmt_utf8(dest?dest+written:dest,todo);
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i+=5;
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prev=-1;
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continue;
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}
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default:
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if (prev!=(unsigned int)-1) return 0; // lead surrogate not followed by tail surrogate
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c=s[i+1];
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break;
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}
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++i;
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}
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if (dest) dest[written]=c;
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++written;
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}
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*destlen=written;
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return i;
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}
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