lavc/bitstream: templatize for BE/LE

Allows using both BE and LE bitstream readers in the same file.

1 files changed, 496 insertions, 0 deletions

diff --git a/libavcodec/bitstream_template.h b/libavcodec/bitstream_template.h
new file mode 100644
index 0000000000..f2c14fc4d3
--- /dev/null
+++ b/libavcodec/bitstream_template.h
@@ -0,0 +1,496 @@
+/*
+ * Copyright (c) 2016 Alexandra Hájková
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifdef BITSTREAM_TEMPLATE_LE
+#   define BS_SUFFIX_LOWER _le
+#   define BS_SUFFIX_UPPER LE
+#else
+#   define BS_SUFFIX_LOWER _be
+#   define BS_SUFFIX_UPPER BE
+#endif
+
+#define BS_JOIN(x, y, z) x ## y ## z
+#define BS_JOIN3(x, y, z) BS_JOIN(x, y, z)
+#define BS_FUNC(x) BS_JOIN3(bits_, x, BS_SUFFIX_LOWER)
+
+#define BSCTX BS_JOIN3(Bitstream, Context, BS_SUFFIX_UPPER)
+
+typedef struct BSCTX {
+    uint64_t bits;       // stores bits read from the buffer
+    const uint8_t *buffer, *buffer_end;
+    const uint8_t *ptr;  // pointer to the position inside a buffer
+    unsigned bits_valid; // number of bits left in bits field
+    unsigned size_in_bits;
+} BSCTX;
+
+/**
+ * @return
+ * - 0 on successful refill
+ * - a negative number when bitstream end is hit
+ *
+ * Always succeeds when UNCHECKED_BITSTREAM_READER is enabled.
+ */
+static inline int BS_FUNC(priv_refill_64)(BSCTX *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+    if (bc->ptr >= bc->buffer_end)
+        return -1;
+#endif
+
+#ifdef BITSTREAM_TEMPLATE_LE
+    bc->bits       = AV_RL64(bc->ptr);
+#else
+    bc->bits       = AV_RB64(bc->ptr);
+#endif
+    bc->ptr       += 8;
+    bc->bits_valid = 64;
+
+    return 0;
+}
+
+/**
+ * @return
+ * - 0 on successful refill
+ * - a negative number when bitstream end is hit
+ *
+ * Always succeeds when UNCHECKED_BITSTREAM_READER is enabled.
+ */
+static inline int BS_FUNC(priv_refill_32)(BSCTX *bc)
+{
+#if !UNCHECKED_BITSTREAM_READER
+    if (bc->ptr >= bc->buffer_end)
+        return -1;
+#endif
+
+#ifdef BITSTREAM_TEMPLATE_LE
+    bc->bits      |= (uint64_t)AV_RL32(bc->ptr) << bc->bits_valid;
+#else
+    bc->bits      |= (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_valid);
+#endif
+    bc->ptr        += 4;
+    bc->bits_valid += 32;
+
+    return 0;
+}
+
+/**
+ * Initialize BitstreamContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bits at once and could read over the end
+ * @param bit_size the size of the buffer in bits
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
+ */
+static inline int BS_FUNC(init)(BSCTX *bc, const uint8_t *buffer,
+                                     unsigned int bit_size)
+{
+    unsigned int buffer_size;
+
+    if (bit_size > INT_MAX - 7 || !buffer) {
+        bc->buffer     = NULL;
+        bc->ptr        = NULL;
+        bc->bits_valid = 0;
+        return AVERROR_INVALIDDATA;
+    }
+
+    buffer_size = (bit_size + 7) >> 3;
+
+    bc->buffer       = buffer;
+    bc->buffer_end   = buffer + buffer_size;
+    bc->ptr          = bc->buffer;
+    bc->size_in_bits = bit_size;
+    bc->bits_valid   = 0;
+    bc->bits         = 0;
+
+    BS_FUNC(priv_refill_64)(bc);
+
+    return 0;
+}
+
+/**
+ * Initialize BitstreamContext.
+ * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
+ *        larger than the actual read bits because some optimized bitstream
+ *        readers read 32 or 64 bits at once and could read over the end
+ * @param byte_size the size of the buffer in bytes
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow
+ */
+static inline int BS_FUNC(init8)(BSCTX *bc, const uint8_t *buffer,
+                                      unsigned int byte_size)
+{
+    if (byte_size > INT_MAX / 8)
+        return AVERROR_INVALIDDATA;
+    return BS_FUNC(init)(bc, buffer, byte_size * 8);
+}
+
+/**
+ * Return number of bits already read.
+ */
+static inline int BS_FUNC(tell)(const BSCTX *bc)
+{
+    return (bc->ptr - bc->buffer) * 8 - bc->bits_valid;
+}
+
+/**
+ * Return buffer size in bits.
+ */
+static inline int BS_FUNC(size)(const BSCTX *bc)
+{
+    return bc->size_in_bits;
+}
+
+/**
+ * Return the number of the bits left in a buffer.
+ */
+static inline int BS_FUNC(left)(const BSCTX *bc)
+{
+    return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_valid;
+}
+
+static inline uint64_t BS_FUNC(priv_val_show)(BSCTX *bc, unsigned int n)
+{
+    av_assert2(n > 0 && n <= 64);
+
+#ifdef BITSTREAM_TEMPLATE_LE
+    return bc->bits & (UINT64_MAX >> (64 - n));
+#else
+    return bc->bits >> (64 - n);
+#endif
+}
+
+static inline void BS_FUNC(priv_skip_remaining)(BSCTX *bc, unsigned int n)
+{
+#ifdef BITSTREAM_TEMPLATE_LE
+    bc->bits >>= n;
+#else
+    bc->bits <<= n;
+#endif
+    bc->bits_valid -= n;
+}
+
+static inline uint64_t BS_FUNC(priv_val_get)(BSCTX *bc, unsigned int n)
+{
+    uint64_t ret;
+
+    av_assert2(n > 0 && n < 64);
+
+    ret = BS_FUNC(priv_val_show)(bc, n);
+    BS_FUNC(priv_skip_remaining)(bc, n);
+
+    return ret;
+}
+
+/**
+ * Return one bit from the buffer.
+ */
+static inline unsigned int BS_FUNC(read_bit)(BSCTX *bc)
+{
+    if (!bc->bits_valid && BS_FUNC(priv_refill_64)(bc) < 0)
+        return 0;
+
+    return BS_FUNC(priv_val_get)(bc, 1);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 1-32 range.
+ * May be faster than bits_read() when n is not a compile-time constant and is
+ * known to be non-zero;
+ */
+static inline uint32_t BS_FUNC(read_nz)(BSCTX *bc, unsigned int n)
+{
+    av_assert2(n > 0 && n <= 32);
+
+    if (n > bc->bits_valid) {
+        if (BS_FUNC(priv_refill_32)(bc) < 0)
+            bc->bits_valid = n;
+    }
+
+    return BS_FUNC(priv_val_get)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-32  range.
+ */
+static inline uint32_t BS_FUNC(read)(BSCTX *bc, unsigned int n)
+{
+    av_assert2(n <= 32);
+
+    if (!n)
+        return 0;
+
+    return BS_FUNC(read_nz)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-63 range.
+ */
+static inline uint64_t BS_FUNC(read_63)(BSCTX *bc, unsigned int n)
+{
+    uint64_t ret = 0;
+    unsigned left = 0;
+
+    av_assert2(n <= 63);
+
+    if (!n)
+        return 0;
+
+    if (n > bc->bits_valid) {
+        left = bc->bits_valid;
+        n   -= left;
+
+        if (left)
+            ret = BS_FUNC(priv_val_get)(bc, left);
+
+        if (BS_FUNC(priv_refill_64)(bc) < 0)
+            bc->bits_valid = n;
+
+    }
+
+#ifdef BITSTREAM_TEMPLATE_LE
+    ret = BS_FUNC(priv_val_get)(bc, n) << left | ret;
+#else
+    ret = BS_FUNC(priv_val_get)(bc, n) | ret << n;
+#endif
+
+    return ret;
+}
+
+/**
+ * Return n bits from the buffer, n has to be in the 0-64 range.
+ */
+static inline uint64_t BS_FUNC(read_64)(BSCTX *bc, unsigned int n)
+{
+    av_assert2(n <= 64);
+
+    if (n == 64) {
+        uint64_t ret = BS_FUNC(read_63)(bc, 63);
+#ifdef BITSTREAM_TEMPLATE_LE
+        return ret | ((uint64_t)BS_FUNC(read_bit)(bc) << 63);
+#else
+        return (ret << 1) | (uint64_t)BS_FUNC(read_bit)(bc);
+#endif
+    }
+    return BS_FUNC(read_63)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer.
+ * n has to be in the 0-32 range.
+ */
+static inline int32_t BS_FUNC(read_signed)(BSCTX *bc, unsigned int n)
+{
+    return sign_extend(BS_FUNC(read)(bc, n), n);
+}
+
+/**
+ * Return n bits from the buffer but do not change the buffer state.
+ * n has to be in the 1-32 range. May
+ */
+static inline uint32_t BS_FUNC(peek_nz)(BSCTX *bc, unsigned int n)
+{
+    av_assert2(n > 0 && n <= 32);
+
+    if (n > bc->bits_valid)
+        BS_FUNC(priv_refill_32)(bc);
+
+    return BS_FUNC(priv_val_show)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer but do not change the buffer state.
+ * n has to be in the 0-32 range.
+ */
+static inline uint32_t BS_FUNC(peek)(BSCTX *bc, unsigned int n)
+{
+    av_assert2(n <= 32);
+
+    if (!n)
+        return 0;
+
+    return BS_FUNC(peek_nz)(bc, n);
+}
+
+/**
+ * Return n bits from the buffer as a signed integer,
+ * do not change the buffer state.
+ * n has to be in the 0-32 range.
+ */
+static inline int BS_FUNC(peek_signed)(BSCTX *bc, unsigned int n)
+{
+    return sign_extend(BS_FUNC(peek)(bc, n), n);
+}
+
+/**
+ * Skip n bits in the buffer.
+ */
+static inline void BS_FUNC(skip)(BSCTX *bc, unsigned int n)
+{
+    if (n < bc->bits_valid)
+        BS_FUNC(priv_skip_remaining)(bc, n);
+    else {
+        n -= bc->bits_valid;
+        bc->bits       = 0;
+        bc->bits_valid = 0;
+
+        if (n >= 64) {
+            unsigned int skip = n / 8;
+
+            n -= skip * 8;
+            bc->ptr += skip;
+        }
+        BS_FUNC(priv_refill_64)(bc);
+        if (n)
+            BS_FUNC(priv_skip_remaining)(bc, n);
+    }
+}
+
+/**
+ * Seek to the given bit position.
+ */
+static inline void BS_FUNC(seek)(BSCTX *bc, unsigned pos)
+{
+    bc->ptr        = bc->buffer;
+    bc->bits       = 0;
+    bc->bits_valid = 0;
+
+    BS_FUNC(skip)(bc, pos);
+}
+
+/**
+ * Skip bits to a byte boundary.
+ */
+static inline const uint8_t *BS_FUNC(align)(BSCTX *bc)
+{
+    unsigned int n = -BS_FUNC(tell)(bc) & 7;
+    if (n)
+        BS_FUNC(skip)(bc, n);
+    return bc->buffer + (BS_FUNC(tell)(bc) >> 3);
+}
+
+/**
+ * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
+ * If MSB not set it is negative.
+ * @param n length in bits
+ */
+static inline int BS_FUNC(read_xbits)(BSCTX *bc, unsigned int n)
+{
+    int32_t cache = BS_FUNC(peek)(bc, 32);
+    int sign = ~cache >> 31;
+    BS_FUNC(priv_skip_remaining)(bc, n);
+
+    return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
+}
+
+/**
+ * Return decoded truncated unary code for the values 0, 1, 2.
+ */
+static inline int BS_FUNC(decode012)(BSCTX *bc)
+{
+    if (!BS_FUNC(read_bit)(bc))
+        return 0;
+    else
+        return BS_FUNC(read_bit)(bc) + 1;
+}
+
+/**
+ * Return decoded truncated unary code for the values 2, 1, 0.
+ */
+static inline int BS_FUNC(decode210)(BSCTX *bc)
+{
+    if (BS_FUNC(read_bit)(bc))
+        return 0;
+    else
+        return 2 - BS_FUNC(read_bit)(bc);
+}
+
+/* Read sign bit and flip the sign of the provided value accordingly. */
+static inline int BS_FUNC(apply_sign)(BSCTX *bc, int val)
+{
+    int sign = BS_FUNC(read_signed)(bc, 1);
+    return (val ^ sign) - sign;
+}
+
+static inline int BS_FUNC(skip_1stop_8data)(BSCTX *s)
+{
+    if (BS_FUNC(left)(s) <= 0)
+        return AVERROR_INVALIDDATA;
+
+    while (BS_FUNC(read_bit)(s)) {
+        BS_FUNC(skip)(s, 8);
+        if (BS_FUNC(left)(s) <= 0)
+            return AVERROR_INVALIDDATA;
+    }
+
+    return 0;
+}
+
+/**
+ * Return the LUT element for the given bitstream configuration.
+ */
+static inline int BS_FUNC(priv_set_idx)(BSCTX *bc, int code, int *n,
+                                             int *nb_bits, const VLCElem *table)
+{
+    unsigned idx;
+
+    *nb_bits = -*n;
+    idx = BS_FUNC(peek)(bc, *nb_bits) + code;
+    *n = table[idx].len;
+
+    return table[idx].sym;
+}
+
+/**
+ * Parse a vlc code.
+ * @param bits is the number of bits which will be read at once, must be
+ *             identical to nb_bits in init_vlc()
+ * @param max_depth is the number of times bits bits must be read to completely
+ *                  read the longest vlc code
+ *                  = (max_vlc_length + bits - 1) / bits
+ * If the vlc code is invalid and max_depth=1, then no bits will be removed.
+ * If the vlc code is invalid and max_depth>1, then the number of bits removed
+ * is undefined.
+ */
+static inline int BS_FUNC(read_vlc)(BSCTX *bc, const VLCElem *table,
+                                         int bits, int max_depth)
+{
+    int nb_bits;
+    unsigned idx = BS_FUNC(peek)(bc, bits);
+    int code     = table[idx].sym;
+    int n        = table[idx].len;
+
+    if (max_depth > 1 && n < 0) {
+        BS_FUNC(priv_skip_remaining)(bc, bits);
+        code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
+        if (max_depth > 2 && n < 0) {
+            BS_FUNC(priv_skip_remaining)(bc, nb_bits);
+            code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
+        }
+    }
+    BS_FUNC(priv_skip_remaining)(bc, n);
+
+    return code;
+}
+
+#undef BSCTX
+#undef BS_FUNC
+#undef BS_JOIN3
+#undef BS_JOIN
+#undef BS_SUFFIX_UPPER
+#undef BS_SUFFIX_LOWER