From 847e56d9e696b813d1cdf3da6d54df5e7b389eae Mon Sep 17 00:00:00 2001 From: David Robillard Date: Fri, 30 Dec 2011 08:10:23 +0000 Subject: Add serd_node_new_blob and serd_base64_decode for handling arbitrary binary data via base64 encoding. git-svn-id: http://svn.drobilla.net/serd/trunk@280 490d8e77-9747-427b-9fa3-0b8f29cee8a0 --- src/string.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) (limited to 'src/string.c') diff --git a/src/string.c b/src/string.c index 968a20e1..a97c6f98 100644 --- a/src/string.c +++ b/src/string.c @@ -112,3 +112,49 @@ serd_strtod(const char* str, char** endptr) *endptr = (char*)s; return result * sign; } + +/** + Base64 decoding table. + This is indexed by encoded characters and returns the numeric value used + for decoding, shifted up by 47 to be in the range of printable ASCII. + A '$' is a placeholder for characters not in the base64 alphabet. +*/ +static const char b64_unmap[255] = + "$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$m$$$ncdefghijkl$$$$$$" + "$/0123456789:;<=>?@ABCDEFGH$$$$$$IJKLMNOPQRSTUVWXYZ[\\]^_`ab$$$$" + "$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$" + "$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$"; + +static inline uint8_t unmap(const uint8_t in) { return b64_unmap[in] - 47; } + +/** + Decode 4 base64 characters to 3 raw bytes. +*/ +static inline size_t +decode_chunk(const uint8_t in[4], uint8_t out[3]) +{ + out[0] = (uint8_t)(((unmap(in[0]) << 2)) | unmap(in[1]) >> 4); + out[1] = (uint8_t)(((unmap(in[1]) << 4) & 0xF0) | unmap(in[2]) >> 2); + out[2] = (uint8_t)(((unmap(in[2]) << 6) & 0xC0) | unmap(in[3])); + return 1 + (in[2] != '=') + ((in[2] != '=') && (in[3] != '=')); +} + +SERD_API +void* +serd_base64_decode(const uint8_t* str, size_t len, size_t* size) +{ + void* buf = malloc((len * 3) / 4 + 2); + *size = 0; + for (size_t i = 0, j = 0; i < len; j += 3) { + uint8_t in[4] = "===="; + size_t n_in = 0; + for (; i < len && n_in < 4; ++n_in) { + for (; i < len && !is_base64(str[i]); ++i) {} // Skip junk + in[n_in] = str[i++]; + } + if (n_in > 1) { + *size += decode_chunk(in, (uint8_t*)buf + j); + } + } + return buf; +} -- cgit v1.2.1