1 files changed, 205 insertions, 0 deletions
diff --git a/dev/hpack/gen-enc.c b/dev/hpack/gen-enc.c
new file mode 100644
index 0000000..3fc5ef9
--- /dev/null
+++ b/dev/hpack/gen-enc.c
@@ -0,0 +1,205 @@
+/*
+ * HPACK encoding table generator. It produces a stream of
+ * <len><idx><name> and a table pointing to the first <len> of each series.
+ * The end of the stream is marked by <len>=0. In parallel, a length-indexed
+ * table is built to access the first entry of each length.
+ *
+ * Build like this :
+ *    gcc -I../../include -o gen-enc gen-enc.c
+ */
+#define HPACK_STANDALONE
+
+#include <ctype.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <import/ist.h>
+#include <haproxy/hpack-tbl-t.h>
+#include "../../src/hpack-tbl.c"
+
+struct idxhdr {
+	const char *ptr;
+	int len;
+	int idx;
+};
+
+struct idxhdr idxhdr[HPACK_SHT_SIZE];
+static int positions[32];
+static char known_hdr[1024];
+
+/* preferred ordering of headers of similar size. Those not mentioned will be
+ * less prioritized.
+ */
+const struct {
+	const char *name;
+	const int rank;
+} ranks[] = {
+	{ .name = "age", .rank = 1 },
+	{ .name = "via", .rank = 2 },
+
+	{ .name = "date", .rank = 1 },
+	{ .name = "host", .rank = 2 },
+
+	{ .name = "accept", .rank = 1 },
+	{ .name = "server", .rank = 2 },
+	{ .name = "cookie", .rank = 3 },
+
+	{ .name = "referer", .rank = 1 },
+	{ .name = "expires", .rank = 2 },
+
+	{ .name = "location", .rank = 1 },
+
+	{ .name = "user-agent", .rank = 1 },
+	{ .name = "set-cookie", .rank = 2 },
+
+	{ .name = "content-type", .rank = 1 },
+
+	{ .name = "cache-control", .rank = 1 },
+	{ .name = "last-modified", .rank = 2 },
+	{ .name = "accept-ranges", .rank = 3 },
+	{ .name = "if-none-match", .rank = 4 },
+
+	{ .name = "content-length", .rank = 1 },
+
+	{ .name = "accept-encoding", .rank = 1 },
+	{ .name = "accept-language", .rank = 2 },
+
+	{ .name = "content-encoding", .rank = 1 },
+
+	{ .name = "transfer-encoding", .rank = 1 },
+	{ .name = "if-modified-since", .rank = 2 },
+
+	{ .name = "content-disposition", .rank = 1 },
+};
+
+/* returns the rank of header <name> or 255 if not found */
+int get_hdr_rank(const char *name)
+{
+	int i;
+
+	for (i = 0; i < sizeof(ranks) / sizeof(ranks[0]); i++) {
+		if (strcmp(ranks[i].name, name) == 0)
+			return ranks[i].rank;
+	}
+	return 255;
+}
+
+/* sorts first on the length, second on the name, and third on the idx, so that
+ * headers which appear with multiple occurrences are always met first.
+ */
+int cmp_idx(const void *l, const void *r)
+{
+	const struct idxhdr *a = l, *b = r;
+	int ranka, rankb;
+	int ret;
+
+	if (a->len < b->len)
+		return -1;
+	else if (a->len > b->len)
+		return 1;
+
+	ranka = get_hdr_rank(a->ptr);
+	rankb = get_hdr_rank(b->ptr);
+
+	if (ranka < rankb)
+		return -1;
+	else if (ranka > rankb)
+		return 1;
+
+	/* same rank, check for duplicates and use index */
+	ret = strcmp(a->ptr, b->ptr);
+	if (ret != 0)
+		return ret;
+
+	if (a->idx < b->idx)
+		return -1;
+	else if (a->idx > b->idx)
+		return 1;
+	else
+		return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int pos;
+	int prev;
+	int len;
+	int i;
+
+	for (len = 0; len < 32; len++)
+		positions[len] = -1;
+
+	for (i = 0; i < HPACK_SHT_SIZE; i++) {
+		idxhdr[i].ptr = hpack_sht[i].n.ptr;
+		idxhdr[i].len = hpack_sht[i].n.len;
+		idxhdr[i].idx = i;
+	}
+
+	/* sorts all header names by length first, then by name, and finally by
+	 * idx so that we meet smaller headers first, that within a length they
+	 * appear in frequency order, and that multiple occurrences appear with
+	 * the smallest index first.
+	 */
+	qsort(&idxhdr[1], HPACK_SHT_SIZE - 1, sizeof(idxhdr[0]), cmp_idx);
+
+	pos = 0;
+	prev = -1;
+	for (i = 1; i < HPACK_SHT_SIZE; i++) {
+		len = idxhdr[i].len;
+		if (len > 31) {
+			//printf("skipping %s (len=%d)\n", idxhdr[i].ptr, idxhdr[i].len);
+			continue;
+		}
+
+		/* first occurrence of this length? */
+		if (positions[len] == -1)
+			positions[len] = pos;
+		else if (prev >= 0 &&
+			 memcmp(&known_hdr[prev] + 2, idxhdr[i].ptr, len) == 0) {
+			/* duplicate header field */
+			continue;
+		}
+
+		/* store <len> <idx> <name> in the output array */
+
+		if (pos + 1 + len + 2 >= sizeof(known_hdr))
+			abort();
+
+		prev = pos;
+		known_hdr[pos++] = len;
+		known_hdr[pos++] = idxhdr[i].idx;
+		memcpy(&known_hdr[pos], idxhdr[i].ptr, len);
+		pos += len;
+		//printf("%d %d %s\n", len, idxhdr[i].idx, idxhdr[i].ptr);
+	}
+
+	if (pos + 1 >= sizeof(known_hdr))
+		abort();
+	known_hdr[pos++] = 0; // size zero ends the stream
+
+	printf("const char hpack_enc_stream[%d] = {\n", pos);
+	for (i = 0; i < pos; i++) {
+		if ((i & 7) == 0)
+			printf("\t /* % 4d: */", i);
+
+		printf(" 0x%02x,", known_hdr[i]);
+
+		if ((i & 7) == 7 || (i == pos - 1))
+			putchar('\n');
+	}
+	printf("};\n\n");
+
+	printf("const signed short hpack_pos_len[32] = {\n");
+	for (i = 0; i < 32; i++) {
+		if ((i & 7) == 0)
+			printf("\t /* % 4d: */", i);
+
+		printf(" % 4d,", positions[i]);
+
+		if ((i & 7) == 7 || (i == pos - 1))
+			putchar('\n');
+	}
+	printf("};\n\n");
+	return 0;
+}