IO: Resolve IO DLL paths from environment variables (#119)

## Summary

Adds a unified mechanism for locating third-party IO DLLs through environment
variables, on top of the existing per-game `[xxxio] path=` INI setting.

## Changes

For each IO DLL, the path is resolved in this order:

1. The section-specific INI value, e.g. `[mai2io] path=`.
2. The section-specific environment variable, e.g. `SEGATOOLS_MAI2IO_PATH`.
3. `SEGATOOLS_IO_ROOT` joined with the default IO DLL filename, e.g.
   `%SEGATOOLS_IO_ROOT%\mai2io.dll`.
4. Empty path, which keeps the built-in IO implementation (unchanged default).

INI and environment-variable paths are run through Windows environment-variable
expansion, so values such as `%SEGATOOLS_IO_ROOT%\mai2io.dll` are valid in the
INI directly.

Reviewed-on: https://gitea.tendokyu.moe/TeamTofuShop/segatools/pulls/119
Co-authored-by: グローランプ <130208311+Gl0w1amp@users.noreply.github.com>
Co-committed-by: グローランプ <130208311+Gl0w1amp@users.noreply.github.com>

common/board/config.c

@@ -11,6 +11,7 @@
 #include "board/vfd.h"
 
 #include "util/dprintf.h"
+#include "util/io-path.h"
 
 // Check windows
 #if _WIN32 || _WIN64
@@ -44,24 +45,26 @@ static void aime_dll_config_load(struct aime_dll_config *cfg, const wchar_t *fil
             // Always empty, due to amdaemon being 64 bit in 32 bit mode
             memset(cfg->path, 0, sizeof(cfg->path));
         #elif defined(ENV64BIT)
-            GetPrivateProfileStringW(
-                    L"aimeio",
-                    L"path",
-                    L"",
+            io_path_config_load(
                     cfg->path,
                     _countof(cfg->path),
+                    L"aimeio",
+                    L"path",
+                    L"SEGATOOLS_AIMEIO_PATH",
+                    L"aimeio.dll",
                     filename);
         #else
             #error "Unknown environment"
         #endif
     } else {
-        GetPrivateProfileStringW(
-            L"aimeio",
-            L"path",
-            L"",
-            cfg->path,
-            _countof(cfg->path),
-            filename);
+        io_path_config_load(
+                cfg->path,
+                _countof(cfg->path),
+                L"aimeio",
+                L"path",
+                L"SEGATOOLS_AIMEIO_PATH",
+                L"aimeio.dll",
+                filename);
     }
 }
 

common/hooklib/config.c

@@ -9,6 +9,7 @@
 #include "hooklib/dvd.h"
 #include "hooklib/y3.h"
 #include "hooklib/y3-dll.h"
+#include "util/io-path.h"
 
 void dvd_config_load(struct dvd_config *cfg, const wchar_t *filename)
 {
@@ -158,12 +159,13 @@ void y3_dll_config_load(
     assert(cfg != NULL);
     assert(filename != NULL);
 
-    GetPrivateProfileStringW(
-            L"y3io",
-            L"path",
-            L"",
+    io_path_config_load(
             cfg->path,
             _countof(cfg->path),
+            L"y3io",
+            L"path",
+            L"SEGATOOLS_Y3IO_PATH",
+            L"y3io.dll",
             filename);
 }
 
@@ -243,4 +245,4 @@ void y3_config_load(
             filename);
 
     wcstombs(cfg->target_code_printer, tmpstr, sizeof(cfg->target_code_printer) - 1);
-}
+}

common/util/io-path.c

@@ -0,0 +1,203 @@
+#include <windows.h>
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+
+#include "util/dprintf.h"
+#include "util/io-path.h"
+
+static bool io_path_expand(
+        wchar_t *out,
+        size_t out_count,
+        const wchar_t *path,
+        const wchar_t *source);
+static bool io_path_from_root(
+        wchar_t *out,
+        size_t out_count,
+        const wchar_t *root_filename);
+static bool io_path_is_separator(wchar_t ch);
+
+bool io_path_config_load(
+        wchar_t *out,
+        size_t out_count,
+        const wchar_t *section,
+        const wchar_t *key,
+        const wchar_t *env_name,
+        const wchar_t *root_filename,
+        const wchar_t *filename)
+{
+    wchar_t path[MAX_PATH];
+    DWORD count;
+
+    assert(out != NULL);
+    assert(out_count > 0);
+    assert(section != NULL);
+    assert(key != NULL);
+    assert(filename != NULL);
+
+    out[0] = L'\0';
+
+    count = GetPrivateProfileStringW(
+            section,
+            key,
+            L"",
+            path,
+            _countof(path),
+            filename);
+
+    if (count >= _countof(path) - 1 && path[0] != L'\0') {
+        dprintf("IO path: INI value [%S] %S may be truncated "
+                "(exceeds %d characters)\n",
+                section,
+                key,
+                (int) _countof(path) - 1);
+    }
+
+    if (path[0] != L'\0') {
+        return io_path_expand(out, out_count, path, key);
+    }
+
+    if (env_name != NULL) {
+        count = GetEnvironmentVariableW(env_name, path, _countof(path));
+
+        if (count >= _countof(path)) {
+            dprintf("IO path: Environment variable too long: %S\n", env_name);
+
+            return false;
+        }
+
+        if (count != 0 && path[0] != L'\0') {
+            return io_path_expand(out, out_count, path, env_name);
+        }
+    }
+
+    return io_path_from_root(out, out_count, root_filename);
+}
+
+static bool io_path_expand(
+        wchar_t *out,
+        size_t out_count,
+        const wchar_t *path,
+        const wchar_t *source)
+{
+    DWORD expanded;
+
+    assert(out != NULL);
+    assert(out_count > 0);
+    assert(path != NULL);
+    assert(source != NULL);
+
+    expanded = ExpandEnvironmentStringsW(path, out, (DWORD) out_count);
+
+    if (expanded == 0) {
+        dprintf("IO path: Failed to expand path from %S: %lx\n",
+                source,
+                GetLastError());
+        out[0] = L'\0';
+
+        return false;
+    }
+
+    if (expanded > out_count) {
+        dprintf("IO path: Expanded path from %S is too long: %S\n",
+                source,
+                path);
+        out[0] = L'\0';
+
+        return false;
+    }
+
+    return true;
+}
+
+static bool io_path_from_root(
+        wchar_t *out,
+        size_t out_count,
+        const wchar_t *root_filename)
+{
+    wchar_t root[MAX_PATH];
+    wchar_t expanded_root[MAX_PATH];
+    size_t root_len;
+    size_t file_len;
+    DWORD count;
+
+    assert(out != NULL);
+    assert(out_count > 0);
+
+    if (root_filename == NULL || root_filename[0] == L'\0') {
+        return false;
+    }
+
+    count = GetEnvironmentVariableW(
+            L"SEGATOOLS_IO_ROOT",
+            root,
+            _countof(root));
+
+    if (count >= _countof(root)) {
+        dprintf("IO path: SEGATOOLS_IO_ROOT is too long\n");
+
+        return false;
+    }
+
+    if (count == 0 || root[0] == L'\0') {
+        return false;
+    }
+
+    if (!io_path_expand(
+            expanded_root,
+            _countof(expanded_root),
+            root,
+            L"SEGATOOLS_IO_ROOT")) {
+        return false;
+    }
+
+    root_len = wcslen(expanded_root);
+    file_len = wcslen(root_filename);
+
+    if (root_len == 0) {
+        return false;
+    }
+
+    if (root_len + file_len + 2 > out_count) {
+        dprintf("IO path: SEGATOOLS_IO_ROOT path is too long: %S\\%S\n",
+                expanded_root,
+                root_filename);
+
+        return false;
+    }
+
+    wcscpy_s(out, out_count, expanded_root);
+
+    if (!io_path_is_separator(out[root_len - 1])) {
+        out[root_len++] = L'\\';
+        out[root_len] = L'\0';
+    }
+
+    wcscat_s(out, out_count, root_filename);
+
+    /* The SEGATOOLS_IO_ROOT fallback is broadcast to every hook at once, so a
+       single global setting is shared by games that may not each ship an IO
+       DLL in that directory. Unlike an explicit INI/env path (direct user
+       intent, allowed to fail loudly at load time), a synthesized root path
+       that does not exist should quietly fall back to the built-in IO
+       implementation instead of aborting hook startup. */
+    if (GetFileAttributesW(out) == INVALID_FILE_ATTRIBUTES) {
+        dprintf("IO path: SEGATOOLS_IO_ROOT DLL not found, "
+                "using built-in IO: %S\n",
+                out);
+        out[0] = L'\0';
+
+        return false;
+    }
+
+    return true;
+}
+
+static bool io_path_is_separator(wchar_t ch)
+{
+    return ch == L'\\' || ch == L'/';
+}

common/util/io-path.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <windows.h>
+
+#include <stdbool.h>
+#include <stddef.h>
+
+bool io_path_config_load(
+        wchar_t *out,
+        size_t out_count,
+        const wchar_t *section,
+        const wchar_t *key,
+        const wchar_t *env_name,
+        const wchar_t *root_filename,
+        const wchar_t *filename);

common/util/meson.build

@@ -21,6 +21,8 @@ util_lib = static_library(
         'fg-detect.h',
         'get_function_ordinal.c',
         'get_function_ordinal.h',
+        'io-path.c',
+        'io-path.h',
         'lib.c',
         'lib.h',
         'slurp.c',