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nghttp2/lib/nghttp2_hd_huffman.c

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+/*
+ * nghttp2 - HTTP/2 C Library
+ *
+ * Copyright (c) 2013 Tatsuhiro Tsujikawa
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "nghttp2_hd_huffman.h"
+
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+
+#include "nghttp2_hd.h"
+#include "nghttp2_net.h"
+
+size_t nghttp2_hd_huff_encode_count(const uint8_t *src, size_t len) {
+  size_t i;
+  size_t nbits = 0;
+
+  for (i = 0; i < len; ++i) {
+    nbits += huff_sym_table[src[i]].nbits;
+  }
+  /* pad the prefix of EOS (256) */
+  return (nbits + 7) / 8;
+}
+
+int nghttp2_hd_huff_encode(nghttp2_bufs *bufs, const uint8_t *src,
+                           size_t srclen) {
+  const nghttp2_huff_sym *sym;
+  const uint8_t *end = src + srclen;
+  uint64_t code = 0;
+  uint32_t x;
+  size_t nbits = 0;
+  size_t avail;
+  int rv;
+
+  avail = nghttp2_bufs_cur_avail(bufs);
+
+  for (; src != end;) {
+    sym = &huff_sym_table[*src++];
+    code |= (uint64_t)sym->code << (32 - nbits);
+    nbits += sym->nbits;
+    if (nbits < 32) {
+      continue;
+    }
+    if (avail >= 4) {
+      x = htonl((uint32_t)(code >> 32));
+      memcpy(bufs->cur->buf.last, &x, 4);
+      bufs->cur->buf.last += 4;
+      avail -= 4;
+      code <<= 32;
+      nbits -= 32;
+      continue;
+    }
+
+    for (; nbits >= 8;) {
+      rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 56));
+      if (rv != 0) {
+        return rv;
+      }
+      code <<= 8;
+      nbits -= 8;
+    }
+
+    avail = nghttp2_bufs_cur_avail(bufs);
+  }
+
+  for (; nbits >= 8;) {
+    rv = nghttp2_bufs_addb(bufs, (uint8_t)(code >> 56));
+    if (rv != 0) {
+      return rv;
+    }
+    code <<= 8;
+    nbits -= 8;
+  }
+
+  if (nbits) {
+    rv = nghttp2_bufs_addb(
+        bufs, (uint8_t)((uint8_t)(code >> 56) | ((1 << (8 - nbits)) - 1)));
+    if (rv != 0) {
+      return rv;
+    }
+  }
+
+  return 0;
+}
+
+void nghttp2_hd_huff_decode_context_init(nghttp2_hd_huff_decode_context *ctx) {
+  ctx->fstate = NGHTTP2_HUFF_ACCEPTED;
+}
+
+ssize_t nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
+                               nghttp2_buf *buf, const uint8_t *src,
+                               size_t srclen, int final) {
+  const uint8_t *end = src + srclen;
+  nghttp2_huff_decode node = {ctx->fstate, 0};
+  const nghttp2_huff_decode *t = &node;
+  uint8_t c;
+
+  /* We use the decoding algorithm described in
+     http://graphics.ics.uci.edu/pub/Prefix.pdf */
+  for (; src != end;) {
+    c = *src++;
+    t = &huff_decode_table[t->fstate & 0x1ff][c >> 4];
+    if (t->fstate & NGHTTP2_HUFF_SYM) {
+      *buf->last++ = t->sym;
+    }
+
+    t = &huff_decode_table[t->fstate & 0x1ff][c & 0xf];
+    if (t->fstate & NGHTTP2_HUFF_SYM) {
+      *buf->last++ = t->sym;
+    }
+  }
+
+  ctx->fstate = t->fstate;
+
+  if (final && !(ctx->fstate & NGHTTP2_HUFF_ACCEPTED)) {
+    return NGHTTP2_ERR_HEADER_COMP;
+  }
+
+  return (ssize_t)srclen;
+}
+
+int nghttp2_hd_huff_decode_failure_state(nghttp2_hd_huff_decode_context *ctx) {
+  return ctx->fstate == 0x100;
+}