ea2b3e6c6f
remove compiler.h include from tryinline.c add #ifdef INTERNAL to files included by n.c and ent.c so they don't need headers in libowfat/ and can compile without an installed or build libowfat
74 lines
2.0 KiB
C
74 lines
2.0 KiB
C
#ifndef INTERNAL
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#include <libowfat/fmt.h>
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#endif
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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=0; i<=0x7fffffff; i=(i<<5)|0x1f, ++j) {
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if (i>=n) {
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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)(((signed 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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#if defined(__i386__) || defined(__x86_64__)
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// on architectures where unaligned writes are ok and don't carry a
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// performance pentalty, it may make sense to not write each byte
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// individually but write a 32-bit word at the end. The downside is that
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// this will write scratch bytes over the bytes following the utf-8. If
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// you allocated a few more bytes scratch space, and did not expect
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// those bytes to be untouched, you can use this function.
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// I did a small benchmark:
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// for (i=j=0; i<1000; i+=fmt_utf8(buf+i,i));
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// Regular fmt_utf8: 13k cpu cycles, fmt_utf_scratch: 11k cpu cycles.
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size_t fmt_utf8_scratch(char *dest,uint32_t n) {
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size_t i;
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unsigned int 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=0; i<=0x7fffffff; i=(i<<5)|0x1f, ++j) {
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if (i>=n) {
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if (dest) {
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uint64_t buf=0;
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while (n>0x3f) {
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buf = (buf << 8) + (n & 0x3f) + 0x80;
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n >>= 6;
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}
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buf = (buf << 8) + (unsigned char)((char)0xc0 >> (j-1)) + n;
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*(uint64_t*)dest = buf;
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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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#endif
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/* unit tested via scan/scan_utf8.c */
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