41 lines
1.2 KiB
C
41 lines
1.2 KiB
C
#ifndef COSMOPOLITAN_LIBC_STR_TPDECODECB_H_
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#define COSMOPOLITAN_LIBC_STR_TPDECODECB_H_
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#include "libc/nexgen32e/bsr.h"
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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/* TODO(jart): DELETE? */
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/**
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* Generic Thompson-Pike Varint Decoder.
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* @return number of bytes successfully consumed or -1 w/ errno
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* @note synchronization is performed
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* @todo delete
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*/
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forceinline int tpdecodecb(wint_t *out, int first,
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int get(void *arg, uint32_t i), void *arg) {
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uint32_t wc, cb, need, msb, j, i = 1;
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if (__builtin_expect((wc = first) == -1, 0)) return -1;
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while (__builtin_expect((wc & 0b11000000) == 0b10000000, 0)) {
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if ((wc = get(arg, i++)) == -1) return -1;
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}
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if (__builtin_expect(!(0 <= wc && wc <= 0x7F), 0)) {
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msb = wc < 252 ? bsr(~wc & 0xff) : 1;
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need = 7 - msb;
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wc &= ((1u << msb) - 1) | 0b00000011;
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for (j = 1; j < need; ++j) {
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if ((cb = get(arg, i++)) == -1) return -1;
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if ((cb & 0b11000000) == 0b10000000) {
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wc = wc << 6 | (cb & 0b00111111);
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} else {
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if (out) *out = u'<EFBFBD>';
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return -1;
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}
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}
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}
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if (__builtin_expect(!!out, 1)) *out = (wint_t)wc;
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return i;
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}
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_LIBC_STR_TPDECODECB_H_ */
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