#ifndef _LZMS_CONSTANTS_H
#define _LZMS_CONSTANTS_H
-#define LZMS_MIN_MATCH_LEN 1
-#define LZMS_MAX_MATCH_LEN 1073809578
+/* Limits on match lengths and offsets (in bytes) */
+#define LZMS_MIN_MATCH_LENGTH 1
+#define LZMS_MAX_MATCH_LENGTH 1073809578
+#define LZMS_MIN_MATCH_OFFSET 1
#define LZMS_MAX_MATCH_OFFSET 1180427428
-#define LZMS_MAX_BUFFER_SIZE (LZMS_MAX_MATCH_OFFSET + 1)
-#define LZMS_NUM_RECENT_OFFSETS 3
-#define LZMS_MAX_INIT_RECENT_OFFSET (LZMS_NUM_RECENT_OFFSETS + 1)
-#define LZMS_OFFSET_OFFSET (LZMS_NUM_RECENT_OFFSETS - 1)
+/* The value to which buffer sizes should be limited. Microsoft's
+ * implementation seems to use 67108864 (2^26) bytes. However, since the format
+ * itself supports higher match lengths and offsets, we'll use 2^30 bytes. */
+#define LZMS_MAX_BUFFER_SIZE 1073741824
+/* The length of each LRU queue for match sources:
+ *
+ * 1. offsets of LZ matches
+ * 2. (power, raw offset) pairs of delta matches */
+#define LZMS_NUM_LZ_REPS 3
+#define LZMS_NUM_DELTA_REPS 3
+
+/* The numbers of binary decision classes needed for encoding queue indices */
+#define LZMS_NUM_LZ_REP_DECISIONS (LZMS_NUM_LZ_REPS - 1)
+#define LZMS_NUM_DELTA_REP_DECISIONS (LZMS_NUM_DELTA_REPS - 1)
+
+/* These are the numbers of probability entries for each binary decision class.
+ * The logarithm base 2 of each of these values is the number of recently
+ * encoded bits that are remembered for each decision class and are used to
+ * select the appropriate probability entry when decoding/encoding the next
+ * binary decision (bit). */
+#define LZMS_NUM_MAIN_PROBS 16
+#define LZMS_NUM_MATCH_PROBS 32
+#define LZMS_NUM_LZ_PROBS 64
+#define LZMS_NUM_LZ_REP_PROBS 64
+#define LZMS_NUM_DELTA_PROBS 64
+#define LZMS_NUM_DELTA_REP_PROBS 64
+
+/* These values define the precision for probabilities in LZMS, which are always
+ * given as a numerator; the denominator is implied. */
#define LZMS_PROBABILITY_BITS 6
-#define LZMS_PROBABILITY_MAX (1U << LZMS_PROBABILITY_BITS)
-#define LZMS_INITIAL_PROBABILITY 48
-#define LZMS_INITIAL_RECENT_BITS 0x0000000055555555ULL
+#define LZMS_PROBABILITY_DENOMINATOR (1 << LZMS_PROBABILITY_BITS)
-#define LZMS_NUM_MAIN_STATES 16
-#define LZMS_NUM_MATCH_STATES 32
-#define LZMS_NUM_LZ_MATCH_STATES 64
-#define LZMS_NUM_LZ_REPEAT_MATCH_STATES 64
-#define LZMS_NUM_DELTA_MATCH_STATES 64
-#define LZMS_NUM_DELTA_REPEAT_MATCH_STATES 64
-#define LZMS_MAX_NUM_STATES 64
+/* These values define the initial state of each probability entry. */
+#define LZMS_INITIAL_PROBABILITY 48
+#define LZMS_INITIAL_RECENT_BITS 0x0000000055555555
+/* The number of symbols in each Huffman-coded alphabet */
#define LZMS_NUM_LITERAL_SYMS 256
#define LZMS_NUM_LENGTH_SYMS 54
#define LZMS_NUM_DELTA_POWER_SYMS 8
#define LZMS_MAX_NUM_OFFSET_SYMS 799
#define LZMS_MAX_NUM_SYMS 799
-#define LZMS_MAX_CODEWORD_LEN 15
-
+/* The rebuild frequencies, in symbols, for each Huffman code */
#define LZMS_LITERAL_CODE_REBUILD_FREQ 1024
#define LZMS_LZ_OFFSET_CODE_REBUILD_FREQ 1024
#define LZMS_LENGTH_CODE_REBUILD_FREQ 512
#define LZMS_DELTA_OFFSET_CODE_REBUILD_FREQ 1024
#define LZMS_DELTA_POWER_CODE_REBUILD_FREQ 512
+/* The maximum length, in bits, of any Huffman codeword. This is guaranteed by
+ * the way frequencies are updated. */
+#define LZMS_MAX_CODEWORD_LENGTH 15
+
+/* The maximum number of verbatim bits, in addition to the Huffman-encoded
+ * length slot symbol, that may be required to encode a match length */
+#define LZMS_MAX_EXTRA_LENGTH_BITS 30
+
+/* The maximum number of verbatim bits, in addition to the Huffman-encoded
+ * offset slot symbol, that may be required to encode a match offset */
+#define LZMS_MAX_EXTRA_OFFSET_BITS 30
+
+/* Parameters for x86 machine code pre/post-processing */
#define LZMS_X86_ID_WINDOW_SIZE 65535
#define LZMS_X86_MAX_TRANSLATION_OFFSET 1023
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