CONTRIB: hpack: implement a reverse huffman table generator for hpack
This one was built by studying the HPACK Huffman table (RFC7541
appendix B). It creates 5 small tables (4*512 bytes, 1*64 bytes) to
map one byte at a time from the input stream based on the following
observations :
* rht_bit31_24[256] is indexed on bits 31..24 when < 0xfe
* rht_bit24_17[256] is indexed on bits 24..17 when 31..24 >= 0xfe
* rht_bit15_11_fe[32] is indexed on bits 15..11 when 24..17 == 0xfe
* rht_bit15_8[256] is indexed on bits 15..8 when 24..17 == 0xff
* rht_bit11_4[256] is indexed on bits 11..4 when 15..8 == 0xff
* when 11..4 == 0xff, 3..2 provide the following mapping :
* 00 => 0x0a, 01 => 0x0d, 10 => 0x16, 11 => EOS
diff --git a/contrib/hpack/gen-rht.c b/contrib/hpack/gen-rht.c
new file mode 100644
index 0000000..b1b9031
--- /dev/null
+++ b/contrib/hpack/gen-rht.c
@@ -0,0 +1,369 @@
+/* Reverse Huffman table generator for HPACK decoder - 2017-05-19 Willy Tarreau
+ *
+ * rht_bit31_24[256] is indexed on bits 31..24 when < 0xfe
+ * rht_bit24_17[256] is indexed on bits 24..17 when 31..24 >= 0xfe
+ * rht_bit15_11_fe[32] is indexed on bits 15..11 when 24..17 == 0xfe
+ * rht_bit15_8[256] is indexed on bits 15..8 when 24..17 == 0xff
+ * rht_bit11_4[256] is indexed on bits 11..4 when 15..8 == 0xff
+ * when 11..4 == 0xff, 3..2 provide the following mapping :
+ * 00 => 0x0a, 01 => 0x0d, 10 => 0x16, 11 => EOS
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* from RFC7541 Appendix B */
+static const struct huff {
+ uint32_t c; /* code point */
+ int b; /* bits */
+} ht[257] = {
+ [0] = { .c = 0x00001ff8, .b = 13 },
+ [1] = { .c = 0x007fffd8, .b = 23 },
+ [2] = { .c = 0x0fffffe2, .b = 28 },
+ [3] = { .c = 0x0fffffe3, .b = 28 },
+ [4] = { .c = 0x0fffffe4, .b = 28 },
+ [5] = { .c = 0x0fffffe5, .b = 28 },
+ [6] = { .c = 0x0fffffe6, .b = 28 },
+ [7] = { .c = 0x0fffffe7, .b = 28 },
+ [8] = { .c = 0x0fffffe8, .b = 28 },
+ [9] = { .c = 0x00ffffea, .b = 24 },
+ [10] = { .c = 0x3ffffffc, .b = 30 },
+ [11] = { .c = 0x0fffffe9, .b = 28 },
+ [12] = { .c = 0x0fffffea, .b = 28 },
+ [13] = { .c = 0x3ffffffd, .b = 30 },
+ [14] = { .c = 0x0fffffeb, .b = 28 },
+ [15] = { .c = 0x0fffffec, .b = 28 },
+ [16] = { .c = 0x0fffffed, .b = 28 },
+ [17] = { .c = 0x0fffffee, .b = 28 },
+ [18] = { .c = 0x0fffffef, .b = 28 },
+ [19] = { .c = 0x0ffffff0, .b = 28 },
+ [20] = { .c = 0x0ffffff1, .b = 28 },
+ [21] = { .c = 0x0ffffff2, .b = 28 },
+ [22] = { .c = 0x3ffffffe, .b = 30 },
+ [23] = { .c = 0x0ffffff3, .b = 28 },
+ [24] = { .c = 0x0ffffff4, .b = 28 },
+ [25] = { .c = 0x0ffffff5, .b = 28 },
+ [26] = { .c = 0x0ffffff6, .b = 28 },
+ [27] = { .c = 0x0ffffff7, .b = 28 },
+ [28] = { .c = 0x0ffffff8, .b = 28 },
+ [29] = { .c = 0x0ffffff9, .b = 28 },
+ [30] = { .c = 0x0ffffffa, .b = 28 },
+ [31] = { .c = 0x0ffffffb, .b = 28 },
+ [32] = { .c = 0x00000014, .b = 6 },
+ [33] = { .c = 0x000003f8, .b = 10 },
+ [34] = { .c = 0x000003f9, .b = 10 },
+ [35] = { .c = 0x00000ffa, .b = 12 },
+ [36] = { .c = 0x00001ff9, .b = 13 },
+ [37] = { .c = 0x00000015, .b = 6 },
+ [38] = { .c = 0x000000f8, .b = 8 },
+ [39] = { .c = 0x000007fa, .b = 11 },
+ [40] = { .c = 0x000003fa, .b = 10 },
+ [41] = { .c = 0x000003fb, .b = 10 },
+ [42] = { .c = 0x000000f9, .b = 8 },
+ [43] = { .c = 0x000007fb, .b = 11 },
+ [44] = { .c = 0x000000fa, .b = 8 },
+ [45] = { .c = 0x00000016, .b = 6 },
+ [46] = { .c = 0x00000017, .b = 6 },
+ [47] = { .c = 0x00000018, .b = 6 },
+ [48] = { .c = 0x00000000, .b = 5 },
+ [49] = { .c = 0x00000001, .b = 5 },
+ [50] = { .c = 0x00000002, .b = 5 },
+ [51] = { .c = 0x00000019, .b = 6 },
+ [52] = { .c = 0x0000001a, .b = 6 },
+ [53] = { .c = 0x0000001b, .b = 6 },
+ [54] = { .c = 0x0000001c, .b = 6 },
+ [55] = { .c = 0x0000001d, .b = 6 },
+ [56] = { .c = 0x0000001e, .b = 6 },
+ [57] = { .c = 0x0000001f, .b = 6 },
+ [58] = { .c = 0x0000005c, .b = 7 },
+ [59] = { .c = 0x000000fb, .b = 8 },
+ [60] = { .c = 0x00007ffc, .b = 15 },
+ [61] = { .c = 0x00000020, .b = 6 },
+ [62] = { .c = 0x00000ffb, .b = 12 },
+ [63] = { .c = 0x000003fc, .b = 10 },
+ [64] = { .c = 0x00001ffa, .b = 13 },
+ [65] = { .c = 0x00000021, .b = 6 },
+ [66] = { .c = 0x0000005d, .b = 7 },
+ [67] = { .c = 0x0000005e, .b = 7 },
+ [68] = { .c = 0x0000005f, .b = 7 },
+ [69] = { .c = 0x00000060, .b = 7 },
+ [70] = { .c = 0x00000061, .b = 7 },
+ [71] = { .c = 0x00000062, .b = 7 },
+ [72] = { .c = 0x00000063, .b = 7 },
+ [73] = { .c = 0x00000064, .b = 7 },
+ [74] = { .c = 0x00000065, .b = 7 },
+ [75] = { .c = 0x00000066, .b = 7 },
+ [76] = { .c = 0x00000067, .b = 7 },
+ [77] = { .c = 0x00000068, .b = 7 },
+ [78] = { .c = 0x00000069, .b = 7 },
+ [79] = { .c = 0x0000006a, .b = 7 },
+ [80] = { .c = 0x0000006b, .b = 7 },
+ [81] = { .c = 0x0000006c, .b = 7 },
+ [82] = { .c = 0x0000006d, .b = 7 },
+ [83] = { .c = 0x0000006e, .b = 7 },
+ [84] = { .c = 0x0000006f, .b = 7 },
+ [85] = { .c = 0x00000070, .b = 7 },
+ [86] = { .c = 0x00000071, .b = 7 },
+ [87] = { .c = 0x00000072, .b = 7 },
+ [88] = { .c = 0x000000fc, .b = 8 },
+ [89] = { .c = 0x00000073, .b = 7 },
+ [90] = { .c = 0x000000fd, .b = 8 },
+ [91] = { .c = 0x00001ffb, .b = 13 },
+ [92] = { .c = 0x0007fff0, .b = 19 },
+ [93] = { .c = 0x00001ffc, .b = 13 },
+ [94] = { .c = 0x00003ffc, .b = 14 },
+ [95] = { .c = 0x00000022, .b = 6 },
+ [96] = { .c = 0x00007ffd, .b = 15 },
+ [97] = { .c = 0x00000003, .b = 5 },
+ [98] = { .c = 0x00000023, .b = 6 },
+ [99] = { .c = 0x00000004, .b = 5 },
+ [100] = { .c = 0x00000024, .b = 6 },
+ [101] = { .c = 0x00000005, .b = 5 },
+ [102] = { .c = 0x00000025, .b = 6 },
+ [103] = { .c = 0x00000026, .b = 6 },
+ [104] = { .c = 0x00000027, .b = 6 },
+ [105] = { .c = 0x00000006, .b = 5 },
+ [106] = { .c = 0x00000074, .b = 7 },
+ [107] = { .c = 0x00000075, .b = 7 },
+ [108] = { .c = 0x00000028, .b = 6 },
+ [109] = { .c = 0x00000029, .b = 6 },
+ [110] = { .c = 0x0000002a, .b = 6 },
+ [111] = { .c = 0x00000007, .b = 5 },
+ [112] = { .c = 0x0000002b, .b = 6 },
+ [113] = { .c = 0x00000076, .b = 7 },
+ [114] = { .c = 0x0000002c, .b = 6 },
+ [115] = { .c = 0x00000008, .b = 5 },
+ [116] = { .c = 0x00000009, .b = 5 },
+ [117] = { .c = 0x0000002d, .b = 6 },
+ [118] = { .c = 0x00000077, .b = 7 },
+ [119] = { .c = 0x00000078, .b = 7 },
+ [120] = { .c = 0x00000079, .b = 7 },
+ [121] = { .c = 0x0000007a, .b = 7 },
+ [122] = { .c = 0x0000007b, .b = 7 },
+ [123] = { .c = 0x00007ffe, .b = 15 },
+ [124] = { .c = 0x000007fc, .b = 11 },
+ [125] = { .c = 0x00003ffd, .b = 14 },
+ [126] = { .c = 0x00001ffd, .b = 13 },
+ [127] = { .c = 0x0ffffffc, .b = 28 },
+ [128] = { .c = 0x000fffe6, .b = 20 },
+ [129] = { .c = 0x003fffd2, .b = 22 },
+ [130] = { .c = 0x000fffe7, .b = 20 },
+ [131] = { .c = 0x000fffe8, .b = 20 },
+ [132] = { .c = 0x003fffd3, .b = 22 },
+ [133] = { .c = 0x003fffd4, .b = 22 },
+ [134] = { .c = 0x003fffd5, .b = 22 },
+ [135] = { .c = 0x007fffd9, .b = 23 },
+ [136] = { .c = 0x003fffd6, .b = 22 },
+ [137] = { .c = 0x007fffda, .b = 23 },
+ [138] = { .c = 0x007fffdb, .b = 23 },
+ [139] = { .c = 0x007fffdc, .b = 23 },
+ [140] = { .c = 0x007fffdd, .b = 23 },
+ [141] = { .c = 0x007fffde, .b = 23 },
+ [142] = { .c = 0x00ffffeb, .b = 24 },
+ [143] = { .c = 0x007fffdf, .b = 23 },
+ [144] = { .c = 0x00ffffec, .b = 24 },
+ [145] = { .c = 0x00ffffed, .b = 24 },
+ [146] = { .c = 0x003fffd7, .b = 22 },
+ [147] = { .c = 0x007fffe0, .b = 23 },
+ [148] = { .c = 0x00ffffee, .b = 24 },
+ [149] = { .c = 0x007fffe1, .b = 23 },
+ [150] = { .c = 0x007fffe2, .b = 23 },
+ [151] = { .c = 0x007fffe3, .b = 23 },
+ [152] = { .c = 0x007fffe4, .b = 23 },
+ [153] = { .c = 0x001fffdc, .b = 21 },
+ [154] = { .c = 0x003fffd8, .b = 22 },
+ [155] = { .c = 0x007fffe5, .b = 23 },
+ [156] = { .c = 0x003fffd9, .b = 22 },
+ [157] = { .c = 0x007fffe6, .b = 23 },
+ [158] = { .c = 0x007fffe7, .b = 23 },
+ [159] = { .c = 0x00ffffef, .b = 24 },
+ [160] = { .c = 0x003fffda, .b = 22 },
+ [161] = { .c = 0x001fffdd, .b = 21 },
+ [162] = { .c = 0x000fffe9, .b = 20 },
+ [163] = { .c = 0x003fffdb, .b = 22 },
+ [164] = { .c = 0x003fffdc, .b = 22 },
+ [165] = { .c = 0x007fffe8, .b = 23 },
+ [166] = { .c = 0x007fffe9, .b = 23 },
+ [167] = { .c = 0x001fffde, .b = 21 },
+ [168] = { .c = 0x007fffea, .b = 23 },
+ [169] = { .c = 0x003fffdd, .b = 22 },
+ [170] = { .c = 0x003fffde, .b = 22 },
+ [171] = { .c = 0x00fffff0, .b = 24 },
+ [172] = { .c = 0x001fffdf, .b = 21 },
+ [173] = { .c = 0x003fffdf, .b = 22 },
+ [174] = { .c = 0x007fffeb, .b = 23 },
+ [175] = { .c = 0x007fffec, .b = 23 },
+ [176] = { .c = 0x001fffe0, .b = 21 },
+ [177] = { .c = 0x001fffe1, .b = 21 },
+ [178] = { .c = 0x003fffe0, .b = 22 },
+ [179] = { .c = 0x001fffe2, .b = 21 },
+ [180] = { .c = 0x007fffed, .b = 23 },
+ [181] = { .c = 0x003fffe1, .b = 22 },
+ [182] = { .c = 0x007fffee, .b = 23 },
+ [183] = { .c = 0x007fffef, .b = 23 },
+ [184] = { .c = 0x000fffea, .b = 20 },
+ [185] = { .c = 0x003fffe2, .b = 22 },
+ [186] = { .c = 0x003fffe3, .b = 22 },
+ [187] = { .c = 0x003fffe4, .b = 22 },
+ [188] = { .c = 0x007ffff0, .b = 23 },
+ [189] = { .c = 0x003fffe5, .b = 22 },
+ [190] = { .c = 0x003fffe6, .b = 22 },
+ [191] = { .c = 0x007ffff1, .b = 23 },
+ [192] = { .c = 0x03ffffe0, .b = 26 },
+ [193] = { .c = 0x03ffffe1, .b = 26 },
+ [194] = { .c = 0x000fffeb, .b = 20 },
+ [195] = { .c = 0x0007fff1, .b = 19 },
+ [196] = { .c = 0x003fffe7, .b = 22 },
+ [197] = { .c = 0x007ffff2, .b = 23 },
+ [198] = { .c = 0x003fffe8, .b = 22 },
+ [199] = { .c = 0x01ffffec, .b = 25 },
+ [200] = { .c = 0x03ffffe2, .b = 26 },
+ [201] = { .c = 0x03ffffe3, .b = 26 },
+ [202] = { .c = 0x03ffffe4, .b = 26 },
+ [203] = { .c = 0x07ffffde, .b = 27 },
+ [204] = { .c = 0x07ffffdf, .b = 27 },
+ [205] = { .c = 0x03ffffe5, .b = 26 },
+ [206] = { .c = 0x00fffff1, .b = 24 },
+ [207] = { .c = 0x01ffffed, .b = 25 },
+ [208] = { .c = 0x0007fff2, .b = 19 },
+ [209] = { .c = 0x001fffe3, .b = 21 },
+ [210] = { .c = 0x03ffffe6, .b = 26 },
+ [211] = { .c = 0x07ffffe0, .b = 27 },
+ [212] = { .c = 0x07ffffe1, .b = 27 },
+ [213] = { .c = 0x03ffffe7, .b = 26 },
+ [214] = { .c = 0x07ffffe2, .b = 27 },
+ [215] = { .c = 0x00fffff2, .b = 24 },
+ [216] = { .c = 0x001fffe4, .b = 21 },
+ [217] = { .c = 0x001fffe5, .b = 21 },
+ [218] = { .c = 0x03ffffe8, .b = 26 },
+ [219] = { .c = 0x03ffffe9, .b = 26 },
+ [220] = { .c = 0x0ffffffd, .b = 28 },
+ [221] = { .c = 0x07ffffe3, .b = 27 },
+ [222] = { .c = 0x07ffffe4, .b = 27 },
+ [223] = { .c = 0x07ffffe5, .b = 27 },
+ [224] = { .c = 0x000fffec, .b = 20 },
+ [225] = { .c = 0x00fffff3, .b = 24 },
+ [226] = { .c = 0x000fffed, .b = 20 },
+ [227] = { .c = 0x001fffe6, .b = 21 },
+ [228] = { .c = 0x003fffe9, .b = 22 },
+ [229] = { .c = 0x001fffe7, .b = 21 },
+ [230] = { .c = 0x001fffe8, .b = 21 },
+ [231] = { .c = 0x007ffff3, .b = 23 },
+ [232] = { .c = 0x003fffea, .b = 22 },
+ [233] = { .c = 0x003fffeb, .b = 22 },
+ [234] = { .c = 0x01ffffee, .b = 25 },
+ [235] = { .c = 0x01ffffef, .b = 25 },
+ [236] = { .c = 0x00fffff4, .b = 24 },
+ [237] = { .c = 0x00fffff5, .b = 24 },
+ [238] = { .c = 0x03ffffea, .b = 26 },
+ [239] = { .c = 0x007ffff4, .b = 23 },
+ [240] = { .c = 0x03ffffeb, .b = 26 },
+ [241] = { .c = 0x07ffffe6, .b = 27 },
+ [242] = { .c = 0x03ffffec, .b = 26 },
+ [243] = { .c = 0x03ffffed, .b = 26 },
+ [244] = { .c = 0x07ffffe7, .b = 27 },
+ [245] = { .c = 0x07ffffe8, .b = 27 },
+ [246] = { .c = 0x07ffffe9, .b = 27 },
+ [247] = { .c = 0x07ffffea, .b = 27 },
+ [248] = { .c = 0x07ffffeb, .b = 27 },
+ [249] = { .c = 0x0ffffffe, .b = 28 },
+ [250] = { .c = 0x07ffffec, .b = 27 },
+ [251] = { .c = 0x07ffffed, .b = 27 },
+ [252] = { .c = 0x07ffffee, .b = 27 },
+ [253] = { .c = 0x07ffffef, .b = 27 },
+ [254] = { .c = 0x07fffff0, .b = 27 },
+ [255] = { .c = 0x03ffffee, .b = 26 },
+ [256] = { .c = 0x3fffffff, .b = 30 }, /* EOS */
+};
+
+
+int main(int argc, char **argv)
+{
+ uint32_t c, i, j;
+
+ /* fill first byte */
+ printf("struct rht rht_bit31_24[256] = {\n");
+ for (j = 0; j < 256; j++) {
+ for (i = 0; i < sizeof(ht)/sizeof(ht[0]); i++) {
+ if (ht[i].b > 8)
+ continue;
+ c = ht[i].c << (32 - ht[i].b);
+
+ if (((c ^ (j << 24)) & -(1 << (32 - ht[i].b)) & 0xff000000) == 0) {
+ printf("\t[0x%02x] = { .c = 0x%02x, .l = %d },\n", j, i, ht[i].b);
+ break;
+ }
+ }
+ }
+ printf("};\n\n");
+
+ printf("struct rht rht_bit24_17[256] = {\n");
+ for (j = 0; j < 256; j++) {
+ for (i = 0; i < sizeof(ht)/sizeof(ht[0]); i++) {
+ if (ht[i].b <= 8 || ht[i].b > 16)
+ continue;
+ c = ht[i].c << (32 - ht[i].b);
+
+ if (((c ^ (j << 17)) & -(1 << (32 - ht[i].b)) & 0x01fe0000) == 0) {
+ printf("\t[0x%02x] = { .c = 0x%02x, .l = %d },\n", j, i, ht[i].b);
+ break;
+ }
+ }
+ }
+ printf("};\n\n");
+
+ printf("struct rht rht_bit15_11_fe[32] = {\n");
+ for (j = 0; j < 32; j++) {
+ for (i = 0; i < sizeof(ht)/sizeof(ht[0]); i++) {
+ if (ht[i].b <= 16 || ht[i].b > 21)
+ continue;
+ c = ht[i].c << (32 - ht[i].b);
+ if ((c & 0x00ff0000) != 0x00fe0000)
+ continue;
+
+ if (((c ^ (j << 11)) & -(1 << (32 - ht[i].b)) & 0x0000f800) == 0) {
+ printf("\t[0x%02x] = { .c = 0x%02x, .l = %d },\n", j, i, ht[i].b);
+ break;
+ }
+ }
+ }
+ printf("};\n\n");
+
+ printf("struct rht rht_bit15_8[256] = {\n");
+ for (j = 0; j < 256; j++) {
+ for (i = 0; i < sizeof(ht)/sizeof(ht[0]); i++) {
+ if (ht[i].b <= 16 || ht[i].b > 24)
+ continue;
+ c = ht[i].c << (32 - ht[i].b);
+ if ((c & 0x00ff0000) != 0x00ff0000)
+ continue;
+
+ if (((c ^ (j << 8)) & -(1 << (32 - ht[i].b)) & 0x0000ff00) == 0) {
+ printf("\t[0x%02x] = { .c = 0x%02x, .l = %d },\n", j, i, ht[i].b);
+ break;
+ }
+ }
+ }
+ printf("};\n\n");
+
+ printf("struct rht rht_bit11_4[256] = {\n");
+ /* fill fourth byte after 0xff 0xff 0xf6-0xff. Only 0xfffffffx are not distinguished */
+ for (j = 0; j < 256; j++) {
+ for (i = 0; i < sizeof(ht)/sizeof(ht[0]); i++) {
+ if (ht[i].b <= 24)
+ continue;
+ c = ht[i].c << (32 - ht[i].b);
+
+ if (((c ^ (j << 4)) & -(1 << (32 - ht[i].b)) & 0x00000ff0) == 0) {
+ //printf("\tj=%02x i=%02x c=%08x l=%d c/l=%08x j/l=%08x xor=%08x\n", j, i, c, ht[i].b, c & -(1 << (32 - ht[i].b)), ((j << 4) & -(1 << (32 - ht[i].b))), (c ^ (j << 4)) & -(1 << (32 - ht[i].b)));
+ printf("\t[0x%02x] = { .c = 0x%02x, .l = %d },\n", j, i, ht[i].b);
+ break;
+ }
+ }
+ }
+ printf("\t/* Note, when l==30, bits 3..2 give 00:0x0a, 01:0x0d, 10:0x16, 11:EOS */\n");
+ printf("};\n\n");
+ return 0;
+}