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115 lines
3.7 KiB
C
115 lines
3.7 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,todo;
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prev=(unsigned int)-1;
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for (i=0; s[i]; ++i) {
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if (s[i]=='"') {
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if (prev!=(unsigned int)-1) goto abort;
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goto done;
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}
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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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// c='\\'; // c already is backslash
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break;
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case '"': c='"'; break;
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case 'n': c='\n'; break;
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case 'r': c='\r'; break;
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case 'b': c='\b'; break;
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case 'f': c='\f'; break;
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case 't': c='\t'; break;
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case 'u':
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{
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size_t j;
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unsigned int cur;
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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) goto abort; // 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) goto abort; // 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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if (prev==(unsigned int)-1) goto abort; // no lead surrogate
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todo=(cur&0x3ff) | ((prev&0x3ff) << 10) | 0x10000;
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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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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 (prev!=(unsigned int)-1) goto abort;
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/* We expect utf-8 incoming. Make sure it's valid. */
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if (!scan_utf8(src+i,4,NULL)) goto abort;
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if (dest) dest[written]=c;
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++written;
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}
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done:
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*destlen=written;
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return i;
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abort:
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if (prev!=(unsigned int)-1) i-=6; // if we abort and there still was an open surrogate pair, cancel it
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*destlen=written;
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return i;
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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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#undef UNITTEST
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#include <scan/scan_fromhex.c>
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#include <scan/scan_utf8.c>
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#include <fmt/fmt_utf8.c>
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int main() {
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char buf[100];
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size_t l;
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assert(scan_jsonescape("fnord",buf,&l)==5 && l==5 && !memcmp(buf,"fnord",5));
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/* is \n properly unescaped? */
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assert(scan_jsonescape("a\\nb",buf,&l)==4 && l==3 && !memcmp(buf,"a\nb",3));
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assert(scan_jsonescape("a\\rb",buf,&l)==4 && l==3 && !memcmp(buf,"a\rb",3));
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assert(scan_jsonescape("a\\bb",buf,&l)==4 && l==3 && !memcmp(buf,"a\bb",3));
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assert(scan_jsonescape("a\\fb",buf,&l)==4 && l==3 && !memcmp(buf,"a\fb",3));
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assert(scan_jsonescape("a\\tb",buf,&l)==4 && l==3 && !memcmp(buf,"a\tb",3));
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assert(scan_jsonescape("a\\\\b",buf,&l)==4 && l==3 && !memcmp(buf,"a\\b",3));
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assert(scan_jsonescape("a\\/b",buf,&l)==4 && l==3 && !memcmp(buf,"a/b",3));
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assert(scan_jsonescape("a\\\"b",buf,&l)==4 && l==3 && !memcmp(buf,"a\"b",3));
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/* does a double quote end the string? */
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assert(scan_jsonescape("a\"b",buf,&l)==1 && l==1 && !memcmp(buf,"a",1));
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/* how about unicode escape */
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assert(scan_jsonescape("a\\u005cb",buf,&l)==8 && l==3 && !memcmp(buf,"a\\b",3));
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/* a trailing surrogate pair with no lead before it */
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assert(scan_jsonescape("a\\udead\"",buf,&l)==1);
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/* a lead surrogate pair with no trailer behind it */
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assert(scan_jsonescape("a\\udafd\"",buf,&l)==1);
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assert(scan_jsonescape("a\\udafd\\udafd",buf,&l)==1);
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assert(scan_jsonescape("a\\udafd0",buf,&l)==1);
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/* correct surrogate pair */
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assert(scan_jsonescape("a\\ud834\\udd1eb",buf,&l)==14 && l==6 && !memcmp(buf,"a\xf0\x9d\x84\x9e""b",6));
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assert(scan_jsonescape("\\ud83d\\udca9x",buf,&l)==13 && l==5 && !memcmp(buf,"\xf0\x9f\x92\xa9x",5));
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/* how about some incorrect UTF-8? */
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assert(scan_jsonescape("a\xc0\xaf",buf,&l)==1 && l==1 && !memcmp(buf,"a",1));
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return 0;
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}
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#endif
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