84 lines
1.7 KiB
Go
84 lines
1.7 KiB
Go
package tape
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import "fmt"
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// TODO: fix #7
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type Tag byte; const (
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SI Tag = 0 << 5 // Small integer
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LI Tag = 1 << 5 // Large unsigned integer
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LSI Tag = 2 << 5 // Large signed integer
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FP Tag = 3 << 5 // Floating point
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SBA Tag = 4 << 5 // Small byte array
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LBA Tag = 5 << 5 // Large byte array
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OTA Tag = 6 << 5 // One-tag array
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KTV Tag = 7 << 5 // Key-tag-value table
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TNMask Tag = 0xE0 // The entire TN bitfield
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CNMask Tag = 0x1F // The entire CN bitfield
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CNLimit Tag = 32 // All valid CNs are < CNLimit
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)
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// what the first nybble of a tag means:
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//
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// 0-1 : SI
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// 2-3 : LI
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// 4-5 : LSI
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// 6-7 : FP
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// 8-9 : SBA
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// A-B : LBA
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// C-D : OTA
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// E-F : KTV
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func (tag Tag) TN() int {
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return int(tag >> 5)
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}
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func (tag Tag) CN() int {
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return int(tag & CNMask)
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}
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func (tag Tag) WithCN(cn int) Tag {
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return (tag & TNMask) | Tag(cn % 32)
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}
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func (tag Tag) WithoutCN() Tag {
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return tag.WithCN(0)
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}
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func (tag Tag) Is(other Tag) bool {
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return tag.TN() == other.TN()
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}
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func (tag Tag) String() string {
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tn := fmt.Sprint(tag.TN())
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switch tag.WithoutCN() {
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case SI: tn = "SI"
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case LI: tn = "LI"
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case LSI: tn = "LSI"
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case FP: tn = "FP"
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case SBA: tn = "SBA"
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case LBA: tn = "LBA"
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case OTA: tn = "OTA"
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case KTV: tn = "KTV"
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}
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return fmt.Sprintf("%s:%d", tn, tag.CN())
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}
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// BufferTag returns the appropriate tag for a buffer.
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func BufferTag(value []byte) Tag {
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return bufferLenTag(len(value))
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}
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// StringTag returns the appropriate tag for a string.
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func StringTag(value string) Tag {
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return bufferLenTag(len(value))
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}
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func bufferLenTag(length int) Tag {
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if length < int(CNLimit) {
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return SBA.WithCN(length)
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} else {
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return LBA.WithCN(IntBytes(uint64(length)) - 1)
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}
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}
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