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Merge pull request #5153 from maxpat78/master
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Calculates true parent's relative path in Differencing VHD locator
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@joncampbell123
joncampbell123 authored Aug 9, 2024
2 parents c557b3d + 31a0d99 commit e2c991b
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Showing 2 changed files with 83 additions and 19 deletions.
1 change: 0 additions & 1 deletion .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -139,4 +139,3 @@ contrib/macos/dosbox-x.plist
# ignore default dosbox config files (used for manual testing)
/dosbox-x.conf
/src/dosbox-x.conf

101 changes: 83 additions & 18 deletions src/ints/bios_vhd.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,57 @@
*
*/

// returns the path of "base" in a form relative to "child"
char* calc_relative_path(const char* base, const char* child) {
#ifndef WIN32
char abs_base[PATH_MAX];
char abs_child[PATH_MAX];
#else
char abs_base[MAX_PATH];
char abs_child[MAX_PATH];
#endif
char* p = abs_base, * q = abs_child, * x, * y, * z;
uint32_t n = 0;

if(!base || !child) return 0;

// retrieves the corresponding absolute paths
#ifndef WIN32
realpath(base, abs_base);
realpath(child, abs_child);
#else
_fullpath(abs_base, base, MAX_PATH);
_fullpath(abs_child, child, MAX_PATH);
#endif
if(!*abs_base || !*abs_child) return 0;

// strips common subpath, if any
while(*p++ == *q++);
p--, q--;
// returns base if they don't share anything
if(!strcmp(p, abs_base)) return strdup(base);
x = q;
// count slashes
while(*x) {
if(*x == '/' || *x == '\\') n++;
x++;
}
// allocates space for the resulting string
y = (char*)malloc(strlen(q) + n * 3 + 2); // n * strlen("..\\")
z = y;
if(!n) {
strcpy(z, ".\\");
z += 2;
}
while(n--) {
strcpy(z, "..\\");
z += 3;
}
strcpy(z, p);
LOG_MSG("%s is base %s relative to child %s", y, base, child);
return y;
}

imageDiskVHD::ErrorCodes imageDiskVHD::Open(const char* fileName, const bool readOnly, imageDisk** disk) {
return Open(fileName, readOnly, disk, nullptr);
}
Expand Down Expand Up @@ -273,6 +324,7 @@ imageDiskVHD::ErrorCodes imageDiskVHD::TryOpenParent(const char* childFileName,

switch (entry.platformCode) {
case 0x57327275:
LOG_MSG("TryOpenParent (W2ru) %s", childFileName);
//Unicode relative pathname (UTF-16) on Windows

#if defined (WIN32) || defined(OS2)
Expand All @@ -295,14 +347,14 @@ imageDiskVHD::ErrorCodes imageDiskVHD::TryOpenParent(const char* childFileName,
return imageDiskVHD::Open(str.c_str(), true, disk, uniqueId);

case 0x57326B75:
LOG_MSG("TryOpenParent (W2ku) %s", childFileName);
//Unicode absolute pathname (UTF-16) on Windows

#if defined (WIN32) || defined(OS2)
/* nothing */
#else
// Linux
// Todo: convert absolute pathname to something applicable for Linux
break;
#endif

//convert byte order, and UTF-16 to ASCII, and change backslashes to slashes if on Linux
Expand Down Expand Up @@ -644,6 +696,7 @@ void imageDiskVHD::SizeToCHS(uint64_t size, uint16_t* c, uint8_t* h, uint8_t* s)

//creates a Dynamic VHD image
uint32_t imageDiskVHD::CreateDynamic(const char* filename, uint64_t size) {
LOG_MSG("CreateDynamic filename=\"%s\"", filename);
uint32_t STATUS = OPEN_SUCCESS;
if(filename == NULL) return ERROR_OPENING;
if(size < 3145728 || size > 2190433320960) // 2040GB is the Windows 11 mounter limit
Expand Down Expand Up @@ -695,6 +748,7 @@ uint32_t imageDiskVHD::CreateDynamic(const char* filename, uint64_t size) {

//creates a Differencing VHD image
uint32_t imageDiskVHD::CreateDifferencing(const char* filename, const char* basename) {
LOG_MSG("CreateDifferencing filename=\"%s\" basename=\"%s\"", filename, basename);
if(filename == NULL || basename == NULL) return ERROR_OPENING;
imageDiskVHD* base_vhd;
if(Open(basename, true, (imageDisk**)&base_vhd) != OPEN_SUCCESS) return ERROR_OPENING_PARENT;
Expand Down Expand Up @@ -732,25 +786,29 @@ uint32_t imageDiskVHD::CreateDifferencing(const char* filename, const char* base
uint32_t table_size = (4 * header.maxTableEntries + 511) / 512 * 512;

//Locators - Windows 11 wants at least the relative W2ru locator, or won't mount!
// we store the absolute pathname to prevent complex depth calculations
#if defined (WIN32)
char absBasePathName[MAX_PATH];
_fullpath(absBasePathName, basename, MAX_PATH);
#else
char absBasePathName[PATH_MAX];
realpath(basename, absBasePathName);
#endif
uint32_t l_basename = strlen(absBasePathName);
uint32_t platsize = (2 * l_basename + 511) / 512 * 512;
header.parentLocatorEntry[0].platformCode = 0x57326B75; //W2ku
header.parentLocatorEntry[0].platformDataLength = 2 * l_basename;
header.parentLocatorEntry[0].platformDataSpace = platsize;
uint32_t len1 = strlen(absBasePathName);
uint32_t plat1 = (2 * len1 + 511) / 512 * 512;
header.parentLocatorEntry[0].platformCode = 0x57326B75; //W2ku (absolute)
header.parentLocatorEntry[0].platformDataLength = 2 * len1;
header.parentLocatorEntry[0].platformDataSpace = plat1;
header.parentLocatorEntry[0].platformDataOffset = 1536 + table_size;

header.parentLocatorEntry[1].platformCode = 0x57327275; // W2ru
header.parentLocatorEntry[1].platformDataLength = 2 * l_basename;
header.parentLocatorEntry[1].platformDataSpace = platsize;
header.parentLocatorEntry[1].platformDataOffset = 2048 + table_size;
// path of parent relative to child
char* relpath = calc_relative_path(basename, filename);

uint32_t len2 = strlen(relpath);
uint32_t plat2 = (2 * len2 + 511) / 512 * 512;
header.parentLocatorEntry[1].platformCode = 0x57327275; // W2ru (relative)
header.parentLocatorEntry[1].platformDataLength = 2 * len2;
header.parentLocatorEntry[1].platformDataSpace = plat2;
header.parentLocatorEntry[1].platformDataOffset = header.parentLocatorEntry[0].platformDataOffset + plat1;

//write dynamic Header
header.checksum = header.CalculateChecksum();
Expand All @@ -768,20 +826,27 @@ uint32_t imageDiskVHD::CreateDifferencing(const char* filename, const char* base
table_size -= 512;
}
//write Parent Locator sectors
uint16_t* w_basename = (uint16_t*)malloc(platsize);
memset(w_basename, 0, platsize);
for(uint32_t i = 0; i < l_basename; i++)
uint16_t* w_basename = (uint16_t*)malloc(plat1);
memset(w_basename, 0, plat1);
for(uint32_t i = 0; i < len1; i++)
//dirty hack to quickly convert ASCII -> UTF-16 *LE* and fix slashes
w_basename[i] = SDL_SwapLE16(absBasePathName[i]=='/'? (uint16_t)'\\' : (uint16_t)absBasePathName[i]);
if (fwrite(w_basename, 1, platsize, vhd) != platsize) STATUS = ERROR_WRITING;
if (fwrite(w_basename, 1, platsize, vhd) != platsize) STATUS = ERROR_WRITING;
w_basename[i] = SDL_SwapLE16(absBasePathName[i] == '/' ? (uint16_t)'\\' : (uint16_t)absBasePathName[i]);
if(fwrite(w_basename, 1, plat1, vhd) != plat1) STATUS = ERROR_WRITING;

w_basename = (uint16_t*)realloc(w_basename, plat2);
memset(w_basename, 0, plat2);
for(uint32_t i = 0; i < len2; i++)
//dirty hack to quickly convert ASCII -> UTF-16 *LE* and fix slashes
w_basename[i] = SDL_SwapLE16(relpath[i] == '/' ? (uint16_t)'\\' : (uint16_t)relpath[i]);
if(fwrite(w_basename, 1, plat2, vhd) != plat2) STATUS = ERROR_WRITING;

//write footer copy
if(fwrite(&footer, 1, 512, vhd) != 512) STATUS = ERROR_WRITING;

delete base_vhd;
free(w_basename);
fclose(vhd);
free(w_basename);
free(relpath);
return STATUS;
}

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