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34 lines
894 B
C
34 lines
894 B
C
#include "fmt.h"
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size_t fmt_utf8(char *dest,uint32_t n) {
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size_t i,j;
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if (n<=0x7f) {
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if (dest) *dest=(char)n;
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return 1;
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}
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for (i=0x3f,j=1; i<=0x7fffffff; i=(i<<5)|0x1f, ++j) {
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if (i>=n) {
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--j;
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if (dest) {
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size_t k=j*6;
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// gcc -fanalyze warns here that j-1 might underflow, leading to
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// undefined behavior because right shift by more than integer
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// width is undefined. That can't happen because both n>0x7f and
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// i>=n would have to be true and we initialize i as 0x3f and
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// with each iteration j is incremented. It's a false positive.
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*dest++=(char)(((char)0xc0 >> (j-1)) | (char)(n >> k));
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while (k) {
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*dest++=(char)(0x80 | ((n >> (k-6)) & 0x3f));
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k-=6;
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}
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}
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return j+1;
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}
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if (i==0x7fffffff) return 0;
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}
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/* we were asked to encode a value that cannot be encoded */
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return 0;
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}
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/* unit tested via scan/scan_utf8.c */
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