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-rw-r--r--modules/brotli/enc/prefix.h53
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diff --git a/modules/brotli/enc/prefix.h b/modules/brotli/enc/prefix.h
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+++ b/modules/brotli/enc/prefix.h
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+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+ Distributed under MIT license.
+ See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Functions for encoding of integers into prefix codes the amount of extra
+ bits, and the actual values of the extra bits. */
+
+#ifndef BROTLI_ENC_PREFIX_H_
+#define BROTLI_ENC_PREFIX_H_
+
+#include "../common/constants.h"
+#include "../common/platform.h"
+#include <brotli/types.h>
+#include "./fast_log.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/* Here distance_code is an intermediate code, i.e. one of the special codes or
+ the actual distance increased by BROTLI_NUM_DISTANCE_SHORT_CODES - 1. */
+static BROTLI_INLINE void PrefixEncodeCopyDistance(size_t distance_code,
+ size_t num_direct_codes,
+ size_t postfix_bits,
+ uint16_t* code,
+ uint32_t* extra_bits) {
+ if (distance_code < BROTLI_NUM_DISTANCE_SHORT_CODES + num_direct_codes) {
+ *code = (uint16_t)distance_code;
+ *extra_bits = 0;
+ return;
+ } else {
+ size_t dist = ((size_t)1 << (postfix_bits + 2u)) +
+ (distance_code - BROTLI_NUM_DISTANCE_SHORT_CODES - num_direct_codes);
+ size_t bucket = Log2FloorNonZero(dist) - 1;
+ size_t postfix_mask = (1u << postfix_bits) - 1;
+ size_t postfix = dist & postfix_mask;
+ size_t prefix = (dist >> bucket) & 1;
+ size_t offset = (2 + prefix) << bucket;
+ size_t nbits = bucket - postfix_bits;
+ *code = (uint16_t)((nbits << 10) |
+ (BROTLI_NUM_DISTANCE_SHORT_CODES + num_direct_codes +
+ ((2 * (nbits - 1) + prefix) << postfix_bits) + postfix));
+ *extra_bits = (uint32_t)((dist - offset) >> postfix_bits);
+ }
+}
+
+#if defined(__cplusplus) || defined(c_plusplus)
+} /* extern "C" */
+#endif
+
+#endif /* BROTLI_ENC_PREFIX_H_ */