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Diffstat (limited to 'src/third-party/base64/lib/arch/neon64/dec_loop.c')
| -rw-r--r-- | src/third-party/base64/lib/arch/neon64/dec_loop.c | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/third-party/base64/lib/arch/neon64/dec_loop.c b/src/third-party/base64/lib/arch/neon64/dec_loop.c new file mode 100644 index 0000000..48232f2 --- /dev/null +++ b/src/third-party/base64/lib/arch/neon64/dec_loop.c @@ -0,0 +1,129 @@ +// The input consists of five valid character sets in the Base64 alphabet, +// which we need to map back to the 6-bit values they represent. +// There are three ranges, two singles, and then there's the rest. +// +// # From To LUT Characters +// 1 [0..42] [255] #1 invalid input +// 2 [43] [62] #1 + +// 3 [44..46] [255] #1 invalid input +// 4 [47] [63] #1 / +// 5 [48..57] [52..61] #1 0..9 +// 6 [58..63] [255] #1 invalid input +// 7 [64] [255] #2 invalid input +// 8 [65..90] [0..25] #2 A..Z +// 9 [91..96] [255] #2 invalid input +// 10 [97..122] [26..51] #2 a..z +// 11 [123..126] [255] #2 invalid input +// (12) Everything else => invalid input + +// The first LUT will use the VTBL instruction (out of range indices are set to +// 0 in destination). +static const uint8_t dec_lut1[] = { + 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, + 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, + 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 255U, 62U, 255U, 255U, 255U, 63U, + 52U, 53U, 54U, 55U, 56U, 57U, 58U, 59U, 60U, 61U, 255U, 255U, 255U, 255U, 255U, 255U, +}; + +// The second LUT will use the VTBX instruction (out of range indices will be +// unchanged in destination). Input [64..126] will be mapped to index [1..63] +// in this LUT. Index 0 means that value comes from LUT #1. +static const uint8_t dec_lut2[] = { + 0U, 255U, 0U, 1U, 2U, 3U, 4U, 5U, 6U, 7U, 8U, 9U, 10U, 11U, 12U, 13U, + 14U, 15U, 16U, 17U, 18U, 19U, 20U, 21U, 22U, 23U, 24U, 25U, 255U, 255U, 255U, 255U, + 255U, 255U, 26U, 27U, 28U, 29U, 30U, 31U, 32U, 33U, 34U, 35U, 36U, 37U, 38U, 39U, + 40U, 41U, 42U, 43U, 44U, 45U, 46U, 47U, 48U, 49U, 50U, 51U, 255U, 255U, 255U, 255U, +}; + +// All input values in range for the first look-up will be 0U in the second +// look-up result. All input values out of range for the first look-up will be +// 0U in the first look-up result. Thus, the two results can be ORed without +// conflicts. +// +// Invalid characters that are in the valid range for either look-up will be +// set to 255U in the combined result. Other invalid characters will just be +// passed through with the second look-up result (using the VTBX instruction). +// Since the second LUT is 64 bytes, those passed-through values are guaranteed +// to have a value greater than 63U. Therefore, valid characters will be mapped +// to the valid [0..63] range and all invalid characters will be mapped to +// values greater than 63. + +static inline void +dec_loop_neon64 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen) +{ + if (*slen < 64) { + return; + } + + // Process blocks of 64 bytes per round. Unlike the SSE codecs, no + // extra trailing zero bytes are written, so it is not necessary to + // reserve extra input bytes: + size_t rounds = *slen / 64; + + *slen -= rounds * 64; // 64 bytes consumed per round + *olen += rounds * 48; // 48 bytes produced per round + + const uint8x16x4_t tbl_dec1 = load_64byte_table(dec_lut1); + const uint8x16x4_t tbl_dec2 = load_64byte_table(dec_lut2); + + do { + const uint8x16_t offset = vdupq_n_u8(63U); + uint8x16x4_t dec1, dec2; + uint8x16x3_t dec; + + // Load 64 bytes and deinterleave: + uint8x16x4_t str = vld4q_u8((uint8_t *) *s); + + // Get indices for second LUT: + dec2.val[0] = vqsubq_u8(str.val[0], offset); + dec2.val[1] = vqsubq_u8(str.val[1], offset); + dec2.val[2] = vqsubq_u8(str.val[2], offset); + dec2.val[3] = vqsubq_u8(str.val[3], offset); + + // Get values from first LUT: + dec1.val[0] = vqtbl4q_u8(tbl_dec1, str.val[0]); + dec1.val[1] = vqtbl4q_u8(tbl_dec1, str.val[1]); + dec1.val[2] = vqtbl4q_u8(tbl_dec1, str.val[2]); + dec1.val[3] = vqtbl4q_u8(tbl_dec1, str.val[3]); + + // Get values from second LUT: + dec2.val[0] = vqtbx4q_u8(dec2.val[0], tbl_dec2, dec2.val[0]); + dec2.val[1] = vqtbx4q_u8(dec2.val[1], tbl_dec2, dec2.val[1]); + dec2.val[2] = vqtbx4q_u8(dec2.val[2], tbl_dec2, dec2.val[2]); + dec2.val[3] = vqtbx4q_u8(dec2.val[3], tbl_dec2, dec2.val[3]); + + // Get final values: + str.val[0] = vorrq_u8(dec1.val[0], dec2.val[0]); + str.val[1] = vorrq_u8(dec1.val[1], dec2.val[1]); + str.val[2] = vorrq_u8(dec1.val[2], dec2.val[2]); + str.val[3] = vorrq_u8(dec1.val[3], dec2.val[3]); + + // Check for invalid input, any value larger than 63: + const uint8x16_t classified + = vcgtq_u8(str.val[0], vdupq_n_u8(63)) + | vcgtq_u8(str.val[1], vdupq_n_u8(63)) + | vcgtq_u8(str.val[2], vdupq_n_u8(63)) + | vcgtq_u8(str.val[3], vdupq_n_u8(63)); + + // Check that all bits are zero: + if (vmaxvq_u8(classified) != 0U) { + break; + } + + // Compress four bytes into three: + dec.val[0] = vshlq_n_u8(str.val[0], 2) | vshrq_n_u8(str.val[1], 4); + dec.val[1] = vshlq_n_u8(str.val[1], 4) | vshrq_n_u8(str.val[2], 2); + dec.val[2] = vshlq_n_u8(str.val[2], 6) | str.val[3]; + + // Interleave and store decoded result: + vst3q_u8((uint8_t *) *o, dec); + + *s += 64; + *o += 48; + + } while (--rounds > 0); + + // Adjust for any rounds that were skipped: + *slen += rounds * 64; + *olen -= rounds * 48; +} |