[mgb] add state info loading support

Author: ITotalJustice

src/mgb/mgb.c

@@ -33,24 +33,6 @@ struct LoadRomConfig
     bool own_fd;
 };
 
-// savestates compressed with defalte/inflate
-// lz4 was considered, but it seemed silly to have 2 compression
-// algorithims included in my code, although lz4 is arguably
-struct StateMeta
-{
-    uint32_t magic;
-    char platform_string[64]; // todo:
-    uint32_t state_size;
-    // if 0, then the state is uncompressed!
-    uint32_t state_compressed_size;
-    uint32_t padding;
-    uint64_t timestamp;
-    uint64_t playtime;
-    uint8_t reserved[160];
-};
-
-enum { STATE_MAGIC = 0x536A0535 };
-
 // struct RewindState
 // {
 //     struct SMS_State state;
@@ -983,3 +965,120 @@ void mgb_set_on_convert_pixels_to_png_format(convert_pixels_to_png_format_func c
 {
     mgb.on_png_convert_cb = cb;
 }
+
+struct StateInfo* mgb_load_state_info_file(const char* path, bool load_png)
+{
+    IFile_t* file = NULL;
+    struct StateInfo* info = NULL;
+    struct StateMeta meta = {0};
+    struct SafeString ss = {0};
+
+    if (!mgb_has_rom())
+    {
+        mgb_log_err("[MGB] tried to load state without rom\n");
+        goto fail;
+    }
+
+    if (path)
+    {
+        strncpy(ss.str, path, sizeof(ss.str) - 1);
+    }
+    else
+    {
+        ss = util_create_state_path(mgb_get_state_folder(), mgb_rom_path());
+    }
+
+    if (!ss_valid(&ss))
+    {
+        goto fail;
+    }
+
+    mgb_log("[MGB] trying to load state from: %s\n", ss.str);
+
+    file = icfile_open(ss.str, IFileMode_READ, 0);
+    if (!file)
+    {
+        mgb_log_err("[MGB] failed to open file: %s\n", ss.str);
+        goto fail;
+    }
+
+    // check for png data by reading header
+    uint8_t png_header[PNG_HEADER_SIZE];
+    if (!ifile_read(file, png_header, sizeof(png_header)))
+    {
+        mgb_log_err("[MGB] failed to read file: %s\n", ss.str);
+        goto fail;
+    }
+
+    const uint32_t png_size = png_get_absolute_size(png_header, sizeof(png_header));
+
+    // skip over png data
+    if (!ifile_seek(file, png_size, SEEK_SET))
+    {
+        mgb_log_err("[MGB] failed to read file: %s\n", ss.str);
+        goto fail;
+    }
+
+    // read meta data
+    if (!ifile_read(file, &meta, sizeof(meta)))
+    {
+        mgb_log_err("[MGB] failed to read file: %s\n", ss.str);
+        goto fail;
+    }
+
+    // todo: check values here...
+    // todo: compare state size with sms
+    if (meta.magic != STATE_MAGIC)
+    {
+        mgb_log("bad state magic...\n");
+        goto fail;
+    }
+
+    info = calloc(1, sizeof(*info));
+    memcpy(&info->meta, &meta, sizeof(meta));
+
+    if (load_png && png_size)
+    {
+        info->png = malloc(png_size);
+        info->png_size = png_size;
+
+        if (!ifile_seek(file, 0, SEEK_SET))
+        {
+            mgb_log_err("[MGB] failed to read file: %s\n", ss.str);
+            goto fail;
+        }
+
+        if (!ifile_read(file, info->png, info->png_size))
+        {
+            mgb_log_err("[MGB] failed to read file: %s\n", ss.str);
+            goto fail;
+        }
+    }
+
+    ifile_close(file);
+
+    return info;
+
+fail:
+    if (file)
+    {
+        ifile_close(file);
+    }
+
+    mgb_free_state_info(info);
+
+    mgb_log_err("[MGB] failed to load state info from: %s\n", ss.str);
+    return NULL;
+}
+
+void mgb_free_state_info(struct StateInfo* info)
+{
+    if (info) {
+        if (info->png) {
+            free(info->png);
+        }
+
+        memset(info, 0, sizeof(*info));
+        free(info);
+    }
+}

src/mgb/mgb.h

@@ -21,6 +21,31 @@ enum CallbackType
     CallbackType_PATCH_ROM,
 };
 
+// savestates compressed with defalte/inflate
+// lz4 was considered, but it seemed silly to have 2 compression
+// algorithims included in my code, although lz4 is arguably
+struct StateMeta
+{
+    uint32_t magic;
+    char platform_string[64]; // todo:
+    uint32_t state_size;
+    // if 0, then the state is uncompressed!
+    uint32_t state_compressed_size;
+    uint32_t padding;
+    uint64_t timestamp;
+    uint64_t playtime;
+    uint8_t reserved[160];
+};
+
+enum { STATE_MAGIC = 0x536A0535 };
+
+struct StateInfo
+{
+    struct StateMeta meta;
+    uint8_t* png;
+    size_t png_size;
+};
+
 #if 0
     #include <stdio.h>
     #define mgb_log(...) fprintf(stdout, __VA_ARGS__)
@@ -82,13 +107,8 @@ bool mgb_patch_rom_data(const char* path, const uint8_t* data, size_t size);
 bool mgb_has_rom(void);
 const char* mgb_rom_path(void);
 
-// bool mgb_rewind_init(size_t frames);
-// void mgb_rewind_close(void);
-
-// save states and stores pixel data for that frame
-// bool mgb_rewind_push_frame(const void* pixels, size_t size);
-// loads state and loads pixel data for that frame
-// bool mgb_rewind_pop_frame(void* pixels, size_t size);
+struct StateInfo* mgb_load_state_info_file(const char* path, bool load_png);
+void mgb_free_state_info(struct StateInfo* info);
 
 #ifdef __cplusplus
 }