// The input consists of six 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 Add Characters // 1 [43] [62] +19 + // 2 [47] [63] +16 / // 3 [48..57] [52..61] +4 0..9 // 4 [65..90] [0..25] -65 A..Z // 5 [97..122] [26..51] -71 a..z // (6) Everything else => invalid input // // We will use lookup tables for character validation and offset computation. // Remember that 0x2X and 0x0X are the same index for _mm_shuffle_epi8, this // allows to mask with 0x2F instead of 0x0F and thus save one constant // declaration (register and/or memory access). // // For offsets: // Perfect hash for lut = ((src >> 4) & 0x2F) + ((src == 0x2F) ? 0xFF : 0x00) // 0000 = garbage // 0001 = / // 0010 = + // 0011 = 0-9 // 0100 = A-Z // 0101 = A-Z // 0110 = a-z // 0111 = a-z // 1000 >= garbage // // For validation, here's the table. // A character is valid if and only if the AND of the 2 lookups equals 0: // // hi \ lo 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 // LUT 0x15 0x11 0x11 0x11 0x11 0x11 0x11 0x11 0x11 0x11 0x13 0x1A 0x1B 0x1B 0x1B 0x1A // // 0000 0x10 char NUL SOH STX ETX EOT ENQ ACK BEL BS HT LF VT FF CR SO SI // andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // // 0001 0x10 char DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC FS GS RS US // andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // // 0010 0x01 char ! " # $ % & ' ( ) * + , - . / // andlut 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x00 0x01 0x01 0x01 0x00 // // 0011 0x02 char 0 1 2 3 4 5 6 7 8 9 : ; < = > ? // andlut 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x02 0x02 0x02 0x02 0x02 0x02 // // 0100 0x04 char @ A B C D E F G H I J K L M N O // andlut 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 // // 0101 0x08 char P Q R S T U V W X Y Z [ \ ] ^ _ // andlut 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x08 0x08 0x08 0x08 0x08 // // 0110 0x04 char ` a b c d e f g h i j k l m n o // andlut 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 // 0111 0x08 char p q r s t u v w x y z { | } ~ // andlut 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x08 0x08 0x08 0x08 0x08 // // 1000 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1001 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1010 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1011 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1100 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1101 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1110 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 // 1111 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 static inline int dec_loop_ssse3_inner (const uint8_t **s, uint8_t **o, size_t *rounds) { const __m128i lut_lo = _mm_setr_epi8( 0x15, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x13, 0x1A, 0x1B, 0x1B, 0x1B, 0x1A); const __m128i lut_hi = _mm_setr_epi8( 0x10, 0x10, 0x01, 0x02, 0x04, 0x08, 0x04, 0x08, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10); const __m128i lut_roll = _mm_setr_epi8( 0, 16, 19, 4, -65, -65, -71, -71, 0, 0, 0, 0, 0, 0, 0, 0); const __m128i mask_2F = _mm_set1_epi8(0x2F); // Load input: __m128i str = _mm_loadu_si128((__m128i *) *s); // Table lookups: const __m128i hi_nibbles = _mm_and_si128(_mm_srli_epi32(str, 4), mask_2F); const __m128i lo_nibbles = _mm_and_si128(str, mask_2F); const __m128i hi = _mm_shuffle_epi8(lut_hi, hi_nibbles); const __m128i lo = _mm_shuffle_epi8(lut_lo, lo_nibbles); // Check for invalid input: if any "and" values from lo and hi are not // zero, fall back on bytewise code to do error checking and reporting: if (_mm_movemask_epi8(_mm_cmpgt_epi8(_mm_and_si128(lo, hi), _mm_setzero_si128())) != 0) { return 0; } const __m128i eq_2F = _mm_cmpeq_epi8(str, mask_2F); const __m128i roll = _mm_shuffle_epi8(lut_roll, _mm_add_epi8(eq_2F, hi_nibbles)); // Now simply add the delta values to the input: str = _mm_add_epi8(str, roll); // Reshuffle the input to packed 12-byte output format: str = dec_reshuffle(str); // Store the output: _mm_storeu_si128((__m128i *) *o, str); *s += 16; *o += 12; *rounds -= 1; return 1; } static inline void dec_loop_ssse3 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen) { if (*slen < 24) { return; } // Process blocks of 16 bytes per round. Because 4 extra zero bytes are // written after the output, ensure that there will be at least 8 bytes // of input data left to cover the gap. (6 data bytes and up to two // end-of-string markers.) size_t rounds = (*slen - 8) / 16; *slen -= rounds * 16; // 16 bytes consumed per round *olen += rounds * 12; // 12 bytes produced per round do { if (rounds >= 8) { if (dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds)) { continue; } break; } if (rounds >= 4) { if (dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds)) { continue; } break; } if (rounds >= 2) { if (dec_loop_ssse3_inner(s, o, &rounds) && dec_loop_ssse3_inner(s, o, &rounds)) { continue; } break; } dec_loop_ssse3_inner(s, o, &rounds); break; } while (rounds > 0); // Adjust for any rounds that were skipped: *slen += rounds * 16; *olen -= rounds * 12; }