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table_segment.go
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/
table_segment.go
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/*
* This file is subject to the terms and conditions defined in
* file 'LICENSE.md', which is part of this source code package.
*/
package segments
import (
"fmt"
"github.com/unidoc/unipdf/v3/internal/jbig2/decoder/huffman"
"github.com/unidoc/unipdf/v3/internal/jbig2/reader"
)
// TableSegment is the model used for user defined Huffman Table Segment - see 7.4.13 and appendix B.
type TableSegment struct {
r reader.StreamReader
// Code Table Flags B.2.1
htOutOfBand int
htPS int
htRS int
// Code Table lowest value B.2.2
htLow int
// Code Table highest value B.2.3
htHight int
}
// Compile time check if the TableSegment implements huffman.BasicTabler.
var _ huffman.BasicTabler = &TableSegment{}
// Init initializes the table segment.
// Implements Segmenter interface.
func (t *TableSegment) Init(h *Header, r reader.StreamReader) error {
t.r = r
return t.parseHeader()
}
// HtPS implements huffman.BasicTabler interface.
func (t *TableSegment) HtPS() int {
return t.htPS
}
// HtRS implements huffman.BasicTabler interface.
func (t *TableSegment) HtRS() int {
return t.htRS
}
// HtLow implements huffman.BasicTabler interface.
func (t *TableSegment) HtLow() int {
return t.htLow
}
// HtHigh implements huffman.BasicTabler interface.
func (t *TableSegment) HtHigh() int {
return t.htHight
}
// HtOOB implements huffman.BasicTabler interface.
func (t *TableSegment) HtOOB() int {
return t.htOutOfBand
}
// StreamReader implements huffman.BasicTabler interface.
func (t *TableSegment) StreamReader() reader.StreamReader {
return t.r
}
func (t *TableSegment) parseHeader() (err error) {
var (
bit int
bits uint64
)
bit, err = t.r.ReadBit()
if err != nil {
return
}
if bit == 1 {
return fmt.Errorf("invalid table segment definition. B.2.1 Code Table flags: Bit 7 must be zero. Was: %d", bit)
}
// Bit 4-6
if bits, err = t.r.ReadBits(3); err != nil {
return
}
t.htRS = (int(bits) + 1) & 0xf
// Bit 1-3
if bits, err = t.r.ReadBits(3); err != nil {
return
}
t.htPS = (int(bits) + 1) & 0xf
// 4 bytes
if bits, err = t.r.ReadBits(32); err != nil {
return
}
t.htLow = int(bits & 0xffffffff)
// 4 bytes
if bits, err = t.r.ReadBits(32); err != nil {
return
}
t.htHight = int(bits & 0xffffffff)
return
}