subsonic-tui/vendor/github.com/hajimehoshi/go-mp3/internal/maindata/huffman.go

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// Copyright 2017 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package maindata
import (
"fmt"
"github.com/hajimehoshi/go-mp3/internal/bits"
"github.com/hajimehoshi/go-mp3/internal/consts"
"github.com/hajimehoshi/go-mp3/internal/frameheader"
"github.com/hajimehoshi/go-mp3/internal/huffman"
"github.com/hajimehoshi/go-mp3/internal/sideinfo"
)
func readHuffman(m *bits.Bits, header frameheader.FrameHeader, sideInfo *sideinfo.SideInfo, mainData *MainData, part_2_start, gr, ch int) error {
// Check that there is any data to decode. If not, zero the array.
if sideInfo.Part2_3Length[gr][ch] == 0 {
for i := 0; i < consts.SamplesPerGr; i++ {
mainData.Is[gr][ch][i] = 0.0
}
return nil
}
// Calculate bit_pos_end which is the index of the last bit for this part.
bit_pos_end := part_2_start + sideInfo.Part2_3Length[gr][ch] - 1
// Determine region boundaries
region_1_start := 0
region_2_start := 0
if (sideInfo.WinSwitchFlag[gr][ch] == 1) && (sideInfo.BlockType[gr][ch] == 2) {
region_1_start = 36 // sfb[9/3]*3=36
region_2_start = consts.SamplesPerGr // No Region2 for short block case.
} else {
sfreq := header.SamplingFrequency()
lsf := header.LowSamplingFrequency()
l := consts.SfBandIndices[lsf][sfreq][consts.SfBandIndicesLong]
i := sideInfo.Region0Count[gr][ch] + 1
if i < 0 || len(l) <= i {
// TODO: Better error messages (#3)
return fmt.Errorf("mp3: readHuffman failed: invalid index i: %d", i)
}
region_1_start = l[i]
j := sideInfo.Region0Count[gr][ch] + sideInfo.Region1Count[gr][ch] + 2
if j < 0 || len(l) <= j {
// TODO: Better error messages (#3)
return fmt.Errorf("mp3: readHuffman failed: invalid index j: %d", j)
}
region_2_start = l[j]
}
// Read big_values using tables according to region_x_start
for is_pos := 0; is_pos < sideInfo.BigValues[gr][ch]*2; is_pos++ {
// #22
if is_pos >= len(mainData.Is[gr][ch]) {
return fmt.Errorf("mp3: is_pos was too big: %d", is_pos)
}
table_num := 0
if is_pos < region_1_start {
table_num = sideInfo.TableSelect[gr][ch][0]
} else if is_pos < region_2_start {
table_num = sideInfo.TableSelect[gr][ch][1]
} else {
table_num = sideInfo.TableSelect[gr][ch][2]
}
// Get next Huffman coded words
x, y, _, _, err := huffman.Decode(m, table_num)
if err != nil {
return err
}
// In the big_values area there are two freq lines per Huffman word
mainData.Is[gr][ch][is_pos] = float32(x)
is_pos++
mainData.Is[gr][ch][is_pos] = float32(y)
}
// Read small values until is_pos = 576 or we run out of huffman data
// TODO: Is this comment wrong?
table_num := sideInfo.Count1TableSelect[gr][ch] + 32
is_pos := sideInfo.BigValues[gr][ch] * 2
for is_pos <= 572 && m.BitPos() <= bit_pos_end {
// Get next Huffman coded words
x, y, v, w, err := huffman.Decode(m, table_num)
if err != nil {
return err
}
mainData.Is[gr][ch][is_pos] = float32(v)
is_pos++
if is_pos >= consts.SamplesPerGr {
break
}
mainData.Is[gr][ch][is_pos] = float32(w)
is_pos++
if is_pos >= consts.SamplesPerGr {
break
}
mainData.Is[gr][ch][is_pos] = float32(x)
is_pos++
if is_pos >= consts.SamplesPerGr {
break
}
mainData.Is[gr][ch][is_pos] = float32(y)
is_pos++
}
// Check that we didn't read past the end of this section
if m.BitPos() > (bit_pos_end + 1) {
// Remove last words read
is_pos -= 4
}
if is_pos < 0 {
is_pos = 0
}
// Setup count1 which is the index of the first sample in the rzero reg.
sideInfo.Count1[gr][ch] = is_pos
// Zero out the last part if necessary
for is_pos < consts.SamplesPerGr {
mainData.Is[gr][ch][is_pos] = 0.0
is_pos++
}
// Set the bitpos to point to the next part to read
m.SetPos(bit_pos_end + 1)
return nil
}