137 lines
3.0 KiB
Go
137 lines
3.0 KiB
Go
package prodos
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import (
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"os"
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)
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func ReadVolumeBitmap(file *os.File) []byte {
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headerBlock := ReadBlock(file, 2)
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volumeHeader := parseVolumeHeader(headerBlock)
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bitmap := make([]byte, volumeHeader.TotalBlocks/8+1)
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totalBitmapBlocks := volumeHeader.TotalBlocks / 8 / 512
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for i := 0; i <= totalBitmapBlocks; i++ {
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bitmapBlock := ReadBlock(file, i+volumeHeader.BitmapStartBlock)
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for j := 0; j < 512; j++ {
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bitmap[i*512+j] = bitmapBlock[j]
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}
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}
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return bitmap
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}
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func WriteVolumeBitmap(file *os.File, bitmap []byte) {
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headerBlock := ReadBlock(file, 2)
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volumeHeader := parseVolumeHeader(headerBlock)
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for i := 0; i < len(bitmap)/512; i++ {
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WriteBlock(file, volumeHeader.BitmapStartBlock+i, bitmap[i*512:i*512+512])
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}
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}
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func CreateVolumeBitmap(numberOfBlocks int) []byte {
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volumeBitmapBlocks := numberOfBlocks / 512 / 8
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if volumeBitmapBlocks*8*512 < numberOfBlocks {
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volumeBitmapBlocks++
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}
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// set all 1's to show blocks available...
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volumeBitmap := make([]byte, volumeBitmapBlocks*512)
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for i := 0; i < len(volumeBitmap); i++ {
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volumeBitmap[i] = 0xFF
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}
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// boot blocks
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MarkBlockInVolumeBitmap(volumeBitmap, 0)
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MarkBlockInVolumeBitmap(volumeBitmap, 1)
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// root directory
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MarkBlockInVolumeBitmap(volumeBitmap, 2)
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MarkBlockInVolumeBitmap(volumeBitmap, 3)
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MarkBlockInVolumeBitmap(volumeBitmap, 4)
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MarkBlockInVolumeBitmap(volumeBitmap, 5)
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// volume bitmap blocks
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for i := 0; i < volumeBitmapBlocks; i++ {
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MarkBlockInVolumeBitmap(volumeBitmap, 6+i)
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}
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// blocks beyond the volume
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totalBlocksInBitmap := volumeBitmapBlocks * 512 * 8
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blocksBeyondEnd := totalBlocksInBitmap - numberOfBlocks
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if blocksBeyondEnd > 0 {
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for i := totalBlocksInBitmap - blocksBeyondEnd; i < totalBlocksInBitmap; i++ {
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MarkBlockInVolumeBitmap(volumeBitmap, i)
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}
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}
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//DumpBlock(volumeBitmap)
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return volumeBitmap
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}
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func FindFreeBlocks(numberOfBlocks int) []int {
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return nil
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}
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func MarkBlockInVolumeBitmap(volumeBitmap []byte, blockNumber int) {
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bitToChange := blockNumber % 8
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byteToChange := blockNumber / 8
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byteToAnd := 0b11111111
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switch bitToChange {
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case 0:
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byteToAnd = 0b01111111
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case 1:
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byteToAnd = 0b10111111
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case 2:
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byteToAnd = 0b11011111
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case 3:
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byteToAnd = 0b11101111
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case 4:
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byteToAnd = 0b11110111
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case 5:
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byteToAnd = 0b11111011
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case 6:
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byteToAnd = 0b11111101
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case 7:
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byteToAnd = 0b11111110
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}
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//fmt.Printf("blockNumber: $%04X byteToWrite: 0b%08b volumeBitmap: $%02X byteToChange: $%04X\n", blockNumber, byteToWrite, volumeBitmap[byteToChange], byteToChange)
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volumeBitmap[byteToChange] &= byte(byteToAnd)
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}
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func FreeBlockInVolumeBitmap(volumeBitmap []byte, blockNumber int) {
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bitToChange := blockNumber % 8
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byteToChange := blockNumber / 8
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byteToOr := 0b00000000
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switch bitToChange {
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case 0:
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byteToOr = 0b10000000
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case 1:
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byteToOr = 0b01000000
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case 2:
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byteToOr = 0b00100000
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case 3:
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byteToOr = 0b00010000
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case 4:
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byteToOr = 0b00001000
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case 5:
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byteToOr = 0b00000100
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case 6:
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byteToOr = 0b00000010
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case 7:
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byteToOr = 0b00000001
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}
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volumeBitmap[byteToChange] |= byte(byteToOr)
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}
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