diff options
Diffstat (limited to 'u8decode.h')
| -rw-r--r-- | u8decode.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/u8decode.h b/u8decode.h new file mode 100644 index 0000000..7599377 --- /dev/null +++ b/u8decode.h @@ -0,0 +1,25 @@ +#include <stdint.h> + +// Decode one UTF-8 codepoint into cp, return number of bytes to next one. +// On invalid UTF-8, return -1, and do not change cp. +// Overlong sequences, surrogates and invalid codepoints are not checked. +// +// This code is meant to be inlined, if cp is unused it can be optimized away. +static int +u8decode(const char *cs, uint32_t *cp) +{ + const uint8_t *s = (uint8_t *)cs; + + if (*s == 0) { *cp = 0; return 0; } + if (*s < 0x80) { *cp = *s; return 1; } + if (*s < 0xc0) { return -1; } + if (*s < 0xe0) { *cp = *s & 0x1f; goto u2; } + if (*s < 0xf0) { *cp = *s & 0x0f; goto u3; } + if (*s < 0xf8) { *cp = *s & 0x07; goto u4; } + return -1; + +u4: if ((*++s & 0xc0) != 0x80) return -1; *cp = (*cp << 6) | (*s & 0x3f); +u3: if ((*++s & 0xc0) != 0x80) return -1; *cp = (*cp << 6) | (*s & 0x3f); +u2: if ((*++s & 0xc0) != 0x80) return -1; *cp = (*cp << 6) | (*s & 0x3f); + return s - (uint8_t *)cs + 1; +} |