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Initial sparse/diff sector writing implementation

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This commit is contained in:
shermp
2019-06-10 23:41:24 +12:00
parent 6a0a614ef0
commit d5ae2604de
1 changed files with 100 additions and 0 deletions
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100
src/minivhd_io.c
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@@ -1,6 +1,7 @@
#include <stdlib.h>
#include <string.h>
#include "minivhd_internal.h"
#include "minivhd_util.h"
#include "minivhd.h"
/* The following bit array macros adapted from
@@ -10,6 +11,13 @@
#define VHD_CLEARBIT(A,k) ( A[(k/8)] &= ~(0x80 >> (k%8)) )
#define VHD_TESTBIT(A,k) ( A[(k/8)] & (0x80 >> (k%8)) )
static inline void mvhd_check_sectors(int offset, int num_sectors, int total_sectors, int* transfer_sect, int* trunc_sect);
static void mvhd_write_empty_sectors(FILE* f, int sector_count);
static void mvhd_read_sect_bitmap(MVHDMeta* vhdm, int blk);
static void mvhd_write_bat_entry(MVHDMeta* vhdm, int blk);
static void mvhd_create_block(MVHDMeta* vhdm, int blk);
static void mvhd_write_sect_bitmap(MVHDMeta* vhdm, int blk);
static inline void mvhd_check_sectors(int offset, int num_sectors, int total_sectors, int* transfer_sect, int* trunc_sect) {
*transfer_sect = num_sectors;
*trunc_sect = 0;
@@ -19,6 +27,13 @@ static inline void mvhd_check_sectors(int offset, int num_sectors, int total_sec
}
}
static void mvhd_write_empty_sectors(FILE* f, int sector_count) {
uint8_t zero_bytes[MVHD_SECTOR_SIZE] = {0};
for (int i = 0; i < sector_count; i++) {
fwrite(zero_bytes, sizeof zero_bytes, 1, f);
}
}
static void mvhd_read_sect_bitmap(MVHDMeta* vhdm, int blk) {
if (!vhdm->block[blk].bitmap_cached) {
if (vhdm->block[blk].bitmap == NULL) {
@@ -32,6 +47,56 @@ static void mvhd_read_sect_bitmap(MVHDMeta* vhdm, int blk) {
}
}
static void mvhd_write_sect_bitmap(MVHDMeta* vhdm, int blk) {
if (vhdm->block[blk].bitmap_cached) {
int64_t abs_offset = vhdm->block[blk].offset * MVHD_SECTOR_SIZE;
fseeko64(vhdm->f, abs_offset, SEEK_SET);
fwrite(vhdm->block[blk].bitmap, MVHD_SECTOR_SIZE, vhdm->bm_sect_count, vhdm->f);
}
}
static void mvhd_write_bat_entry(MVHDMeta* vhdm, int blk) {
uint64_t table_offset = vhdm->sparse.bat_offset + (blk * sizeof vhdm->block[blk].offset);
fseeko64(vhdm->f, table_offset, SEEK_SET);
fwrite(&vhdm->block[blk].offset, sizeof vhdm->block[blk].offset, 1, vhdm->f);
}
static void mvhd_create_block(MVHDMeta* vhdm, int blk) {
uint8_t footer[MVHD_FOOTER_SIZE];
/* Seek to where the footer SHOULD be */
fseeko64(vhdm->f, -MVHD_FOOTER_SIZE, SEEK_END);
fread(footer, sizeof footer, 1, vhdm->f);
fseeko64(vhdm->f, -MVHD_FOOTER_SIZE, SEEK_END);
if (!mvhd_is_conectix_str(footer)) {
/* Oh dear. We use the header instead, since something has gone wrong at the footer */
fseeko64(vhdm->f, 0, SEEK_SET);
fread(footer, sizeof footer, 1, vhdm->f);
fseeko64(vhdm->f, 0, SEEK_END);
}
int64_t abs_offset = ftello64(vhdm->f);
if (abs_offset % MVHD_SECTOR_SIZE != 0) {
/* Yikes! We're supposed to be on a sector boundary. Add some padding */
int64_t padding_amount = (int64_t)MVHD_SECTOR_SIZE - (abs_offset % MVHD_SECTOR_SIZE);
uint8_t zero_byte = 0;
for (int i = 0; i < padding_amount; i++) {
fwrite(&zero_byte, sizeof zero_byte, 1, vhdm->f);
}
abs_offset += padding_amount;
}
int sect_offset = (int)(abs_offset / MVHD_SECTOR_SIZE);
int blk_size_sectors = vhdm->sparse.block_sz / MVHD_SECTOR_SIZE;
mvhd_write_empty_sectors(vhdm->f, vhdm->bm_sect_count + blk_size_sectors);
/* Add a bit of padding. That's what Windows appears to do, although it's not strictly necessary... */
mvhd_write_empty_sectors(vhdm->f, 5);
/* And we finish with the footer */
fwrite(footer, sizeof footer, 1, vhdm->f);
/* We no longer have a sparse block. Update that BAT! */
vhdm->block[blk].offset = sect_offset;
vhdm->block[blk].bitmap = calloc(vhdm->bm_sect_count, MVHD_SECTOR_SIZE);
vhdm->block[blk].bitmap_cached = true;
mvhd_write_bat_entry(vhdm, blk);
}
int mvhd_fixed_read(MVHDMeta* vhdm, int offset, int num_sectors, void* out_buff) {
int64_t addr;
int transfer_sectors, truncated_sectors;
@@ -109,4 +174,39 @@ int mvhd_fixed_write(MVHDMeta* vhdm, int offset, int num_sectors, void* in_buff)
fseeko64(vhdm->f, addr, SEEK_SET);
fwrite(in_buff, transfer_sectors*MVHD_SECTOR_SIZE, 1, vhdm->f);
return truncated_sectors;
}
int mvhd_sparse_diff_write(MVHDMeta* vhdm, int offset, int num_sectors, void* in_buff) {
int transfer_sectors, truncated_sectors;
int total_sectors = vhdm->footer.geom.cyl * vhdm->footer.geom.heads * vhdm->footer.geom.spt;
mvhd_check_sectors(offset, num_sectors, total_sectors, &transfer_sectors, &truncated_sectors);
uint8_t* buff = (uint8_t*)in_buff;
int64_t addr;
int s, ls, blk, prev_blk, blk_count, sib;
ls = offset + transfer_sectors;
prev_blk = -1;
blk_count = 0;
for (s = offset; s <= ls; s++) {
blk = s / vhdm->sect_per_block;
sib = s % vhdm->sect_per_block;
if (vhdm->block[blk].offset == MVHD_SPARSE_BLK) {
mvhd_create_block(vhdm, blk);
}
if (blk != prev_blk) {
blk_count++;
prev_blk = blk;
mvhd_read_sect_bitmap(vhdm, blk);
addr = (int64_t)((vhdm->block[blk].offset + vhdm->bm_sect_count + sib) * MVHD_SECTOR_SIZE);
fseeko64(vhdm->f, addr, SEEK_SET);
}
fwrite(buff, MVHD_SECTOR_SIZE, 1, vhdm->f);
VHD_SETBIT(vhdm->block[blk].bitmap, sib);
buff += MVHD_SECTOR_SIZE;
}
int init_blk = (offset / vhdm->sect_per_block);
for (int i = 0; i < blk_count; i++) {
mvhd_write_sect_bitmap(vhdm, init_blk);
init_blk++;
}
return truncated_sectors;
}