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/* Copyright (C) 2022 June McEnroe <june@causal.agency>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <SDL_rwops.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static void errx(int eval, const char *fmt, ...) {
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
putc('\n', stderr);
exit(eval);
}
static void err(int eval, const char *fmt, ...) {
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
fprintf(stderr, ": %s\n", SDL_GetError());
exit(eval);
}
int main(int argc, char *argv[]) {
if (argc < 2) return 1;
const char *exePath = argv[1];
const char *name = strrchr(exePath, '/');
name = (name ? &name[1] : exePath);
char icoPath[256];
snprintf(
icoPath, sizeof(icoPath), "%.*s.ICO", (int)strcspn(name, "."), name
);
SDL_RWops *exe = SDL_RWFromFile(exePath, "rb");
if (!exe) err(1, "%s", exePath);
// Read the EXE header
if (SDL_ReadU8(exe) != 'M' || SDL_ReadU8(exe) != 'Z') {
errx(1, "%s: invalid MZ signature", exePath);
}
SDL_RWseek(exe, 0x3C, RW_SEEK_SET);
Uint16 neOffset = SDL_ReadLE16(exe);
SDL_RWseek(exe, neOffset, RW_SEEK_SET);
Uint8 sig[2] = { SDL_ReadU8(exe), SDL_ReadU8(exe) };
if (sig[0] == 'P' && sig[1] == 'E') {
errx(1, "%s: not implemented for PE", exePath);
}
if (sig[0] != 'N' || sig[1] != 'E') {
errx(1, "%s: invalid NE/PE signature", exePath);
}
// Read the NE header
SDL_RWseek(exe, neOffset + 0x24, RW_SEEK_SET);
Uint16 resourceTableOffset = neOffset + SDL_ReadLE16(exe);
// Find the RT_GROUP_ICON resource
SDL_RWseek(exe, resourceTableOffset, RW_SEEK_SET);
Uint16 alignmentShift = SDL_ReadLE16(exe);
for (;;) {
Uint16 typeID = SDL_ReadLE16(exe);
Uint16 count = SDL_ReadLE16(exe);
SDL_ReadLE32(exe); // reserved
if (!typeID) {
errx(1, "%s: no group icon resource", exePath);
}
if (typeID == 0x800E) break;
SDL_RWseek(exe, 0x0C * count, RW_SEEK_CUR);
}
SDL_RWops *ico = SDL_RWFromFile(icoPath, "wb");
if (!ico) err(1, "%s", icoPath);
// Copy the ICONHEADER
// https://devblogs.microsoft.com/oldnewthing/20101018-00/?p=12513
SDL_RWseek(exe, (Uint32)SDL_ReadLE16(exe) << alignmentShift, RW_SEEK_SET);
SDL_WriteLE16(ico, SDL_ReadLE16(exe)); // reserved
SDL_WriteLE16(ico, SDL_ReadLE16(exe)); // type
Uint16 iconDirCount = SDL_ReadLE16(exe);
SDL_WriteLE16(ico, iconDirCount);
// Copy ICONDIRENTRY's. The entries in the RT_GROUP_ICON resource differ
// from those in ICO in their last field. In ICO, it is a 32-bit offset
// of the icon data in the ICO file. In the resource, it is a 16-bit
// resource ID of an RT_ICON resource. Here we assume the resources are
// in the same order as the entries referencing them. We translate the
// resource IDs into data offsets by simply tallying up the data lengths
// so far. The data offsets need to be aligned to alignmentShift to match
// up with the lengths of the icon resources.
Uint32 iconDirLength = 0x06 + 0x10 * iconDirCount;
Uint32 dataOffset = iconDirLength;
dataOffset += -dataOffset & ((1 << alignmentShift) - 1);
for (Uint16 i = 0; i < iconDirCount; ++i) {
SDL_WriteU8(ico, SDL_ReadU8(exe)); // width
SDL_WriteU8(ico, SDL_ReadU8(exe)); // height
SDL_WriteU8(ico, SDL_ReadU8(exe)); // colors
SDL_WriteU8(ico, SDL_ReadU8(exe)); // reserved
SDL_WriteLE16(ico, SDL_ReadLE16(exe)); // color planes
SDL_WriteLE16(ico, SDL_ReadLE16(exe)); // bits per pixel
Uint32 dataLength = SDL_ReadLE32(exe);
SDL_ReadLE16(exe); // resource ID, assumed sequential
SDL_WriteLE32(ico, dataLength);
SDL_WriteLE32(ico, dataOffset);
dataOffset += dataLength;
dataOffset += -dataOffset & ((1 << alignmentShift) - 1);
}
// Padding before the first aligned data offset
for (
Uint32 i = 0;
i < (-iconDirLength & ((1 << alignmentShift) - 1));
++i
) {
SDL_WriteU8(ico, 0);
}
// Find the RT_ICON resources
SDL_RWseek(exe, resourceTableOffset + 0x02, RW_SEEK_SET);
Uint16 resourceCount;
for (;;) {
Uint16 typeID = SDL_ReadLE16(exe);
resourceCount = SDL_ReadLE16(exe);
SDL_ReadLE32(exe); // reserved
if (!typeID) {
errx(1, "%s: no icon resources", exePath);
}
if (typeID == 0x8003) break;
SDL_RWseek(exe, 0x0C * resourceCount, RW_SEEK_CUR);
}
// Copy all icon data sequentially
Uint8 *data = NULL;
for (Uint16 i = 0; i < resourceCount; ++i) {
Uint32 dataOffset = (Uint32)SDL_ReadLE16(exe) << alignmentShift;
Uint32 dataLength = (Uint32)SDL_ReadLE16(exe) << alignmentShift;
SDL_ReadLE16(exe); // flags
SDL_ReadLE16(exe); // resource ID
SDL_ReadLE32(exe); // reserved
Sint64 nextResource = SDL_RWtell(exe);
if (nextResource < 0) err(1, "%s", exePath);
SDL_RWseek(exe, dataOffset, RW_SEEK_SET);
data = realloc(data, dataLength);
if (!data) errx(1, "malloc failed");
size_t num = SDL_RWread(exe, data, dataLength, 1);
if (!num) err(1, "%s", exePath);
num = SDL_RWwrite(ico, data, dataLength, 1);
if (!num) err(1, "%s", icoPath);
SDL_RWseek(exe, nextResource, RW_SEEK_SET);
}
free(data);
SDL_RWclose(ico);
SDL_RWclose(exe);
}
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