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Initial commit.
This commit is contained in:
Christopher Kobayashi
parent
1d9a98569f
commit
0fe280bc5a
10
Makefile
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10
Makefile
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CFLAGS= -O2 -Wall -Werror
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all: dc42cksm
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install: all
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install -m755 dc42cksm /usr/local/bin/
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clean:
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rm -f dc42cksm *.o
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220
dc42cksm.c
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dc42cksm.c
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/* dc42cksm
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A command-line program to view the checksums in a Macintosh Disk Copy 4.2
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disk image file, and optionally to update the checksums if they’re not
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correct.
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Originally written by Steve Chamberlin <steve@bigmessowires.com>
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64-bit-cleaned and lightly converted from C++ to C by Christopher RYU
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <malloc.h>
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#include <sys/types.h>
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u_int8_t Read8(FILE* file)
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{
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u_int8_t b;
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fread(&b, 1, 1, file);
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return b;
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}
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u_int16_t ReadBigEndian16(FILE* file)
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{
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u_int8_t b[2];
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fread(&b, 1, 2, file);
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return (((u_int16_t)b[0]) << 8) | b[1];
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}
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u_int32_t ReadBigEndian32(FILE* file)
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{
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u_int8_t b[4];
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fread(&b, 1, 4, file);
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return (((u_int32_t)b[0]) << 24) | (((u_int32_t)b[1]) << 16) | (((u_int32_t)b[2]) << 8) | b[3];
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}
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void SetBigEndian32(u_int8_t* pDest, u_int32_t value)
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{
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pDest[0] = (value >> 24) & 0xFF;
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pDest[1] = (value >> 16) & 0xFF;
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pDest[2] = (value >> 8) & 0xFF;
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pDest[3] = value & 0xFF;
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}
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int main(int argc, char* argv[])
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{
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/* parse the command line */
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if (argc != 2)
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{
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printf("Disk Copy 4.2 checksum tool:\nVerifies and optionally updates checksums for DC42 disk image files.\n\n");
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printf("Usage: %s filename\n", argv[0]);
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return -1;
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}
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char *sourceFilename = argv[1];
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printf("Verifying Disk Copy 4.2 disk image checksums for %s\n", sourceFilename);
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FILE *pFile = fopen(sourceFilename, "rb");
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if (!pFile)
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{
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printf("Could not open source file %s\n", sourceFilename);
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return -1;
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}
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/* check the DC42 signature bytes */
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fseek(pFile, 0x52, SEEK_SET);
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u_int16_t magic0 = Read8(pFile);
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u_int16_t magic1 = Read8(pFile);
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if (magic0 != 1 || magic1 != 0)
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{
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printf("This doesn't look like a valid DC42 disk image file. Aborting.\n");
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fclose(pFile);
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return 0;
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}
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/* return to start */
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fseek(pFile, 0, SEEK_SET);
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/* disk image name */
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u_int8_t nameLen = Read8(pFile);
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unsigned char name[64];
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fread(name, 1, 63, pFile);
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if (nameLen < 64)
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name[nameLen] = 0;
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else
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name[63] = 0;
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printf(" stored image name: %s\n", name);
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/* size of data and tag regions */
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u_int32_t dataSize = ReadBigEndian32(pFile);
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printf(" data size: %08X\n", dataSize);
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u_int32_t tagSize = ReadBigEndian32(pFile);
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printf(" tag size: %08X\n", tagSize);
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/* stored checksums */
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u_int32_t storedDataChecksum = ReadBigEndian32(pFile);
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u_int32_t storedTagChecksum = ReadBigEndian32(pFile);
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/* disk encoding */
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u_int8_t encoding = Read8(pFile);
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switch (encoding)
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{
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case 0:
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printf(" encoding: 00, GCR single-sided double density 400K\n");
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break;
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case 1:
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printf(" encoding: 01, GCR double-sided double density 800K\n");
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break;
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case 2:
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printf(" encoding: 02, MFM double-sided double density 720K\n");
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break;
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case 3:
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printf(" encoding: 03, MFM double-sided high density 1440K\n");
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break;
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default:
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printf(" encoding: %02X, unknown\n", encoding);
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break;
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}
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/* disk format */
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u_int8_t format = Read8(pFile);
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switch (format)
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{
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case 0x02:
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printf(" format: 02, Macintosh/Lisa 400K\n");
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break;
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case 0x22:
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printf(" format: 22, Macintosh 800K\n");
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break;
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case 0x24:
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printf(" format: 24, ProDOS 800K\n");
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break;
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default:
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printf(" format: %02X, unknown\n", format);
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break;
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}
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/* ignore the magic number */
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ReadBigEndian16(pFile);
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/* compute the data checksum */
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u_int32_t dataChecksum = 0;
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for (u_int32_t i=0; i<dataSize; i+=2)
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{
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dataChecksum += ReadBigEndian16(pFile);
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dataChecksum = (dataChecksum >> 1) | ((dataChecksum & 1) << 31);
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}
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/* compute the tag checksum */
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u_int32_t tagChecksum = 0;
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if (tagSize > 12)
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{
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/* skip the first 12 tag bytes */
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for (int i=0; i<12; i++)
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{
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Read8(pFile);
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}
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for (u_int32_t i=12; i<tagSize; i+=2)
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{
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tagChecksum += ReadBigEndian16(pFile);
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tagChecksum = (tagChecksum >> 1) | ((tagChecksum & 1) << 31);
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}
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}
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/* show the results */
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printf(" stored data checksum: %08X\n", storedDataChecksum);
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printf("computed data checksum: %08X\n", dataChecksum);
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printf(" stored tag checksum: %08X\n", storedTagChecksum);
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printf(" computed tag checksum: %08X\n", tagChecksum);
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if (storedDataChecksum == dataChecksum && storedTagChecksum == tagChecksum)
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{
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printf("\nVerification succeeded, no errors.\n");
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}
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else
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{
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printf("\nThe stored checksums do not match the computed checksums.\n");
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printf("\nUpdate the stored checksums? (Y/N) ");
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u_int8_t a = getchar();
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if (a == 'y' || a =='Y')
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{
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/* read the whole file into memory */
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u_int32_t bufSize = 0x54 + dataSize + tagSize;
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u_int8_t* pBuffer = (u_int8_t*)malloc(bufSize);
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if (pBuffer == 0)
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{
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printf("error: couldn't allocate %u bytes\n", bufSize);
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return -1;
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}
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fseek(pFile, 0, SEEK_SET);
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fread(pBuffer, bufSize, 1, pFile);
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fclose(pFile);
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/* modify the checksums */
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SetBigEndian32(&pBuffer[0x48], dataChecksum);
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SetBigEndian32(&pBuffer[0x4C], tagChecksum);
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/* write the modified file */
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FILE *pFile = fopen(sourceFilename, "wb");
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if (!pFile)
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{
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printf("error: could not re-open file for writing\n");
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return -1;
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}
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fwrite(pBuffer, bufSize, 1, pFile);
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printf("%s was modified, checksums updated.\n", sourceFilename);
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}
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else
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{
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printf("%s was not modified.\n", sourceFilename);
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}
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}
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fclose(pFile);
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return 0;
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}
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