From e943a6867f0e37f5eb68e9911a1971f747ed7531 Mon Sep 17 00:00:00 2001
From: TazyFoundSoup <gardendistrict0x0@outlook.com>
Date: Fri, 19 Dec 2025 17:20:02 +1100
Subject: feat(png): add ff_next_chunk function

---
 src/format/image/png.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 57 insertions(+), 2 deletions(-)

(limited to 'src/format/image')

diff --git a/src/format/image/png.c b/src/format/image/png.c
index 6adfe86..266f4f6 100644
--- a/src/format/image/png.c
+++ b/src/format/image/png.c
@@ -5,13 +5,13 @@ ff_result ff_png_isvalid(FILE *file)
 {
     char raw_sig[8];
     if (fread(raw_sig, sizeof(char), 8, file) != 8) {
-        // Inable to read first 8 bytes
+        // Unable to read first 8 bytes
         fclose(file);
         return FF_RESULT_ERROR_INVALID_FILE;
     }
 
     if (memcmp(raw_sig, PNG_SIGNATURE, 8) != 0) {
-        // Signiture did not match
+        // Signature did not match
         fclose(file);
         return FF_RESULT_ERROR_INVALID_FILE_SIGNITURE;
     }
@@ -34,4 +34,59 @@ ff_result ff_open_png(const char *filepath, ff_png_ctx **out_ctx) {
     }
 
     // TODO: Parse
+}
+
+ff_result ff_next_chunk(FILE *file, ff_png_chunk **out_chunk) {
+    // 1. Read length (4 bytes): We have to read the first 4 bytes to know how many bytes to read for data
+    uint32_t length_buffer;
+
+    if (fread(&length_buffer, sizeof(sizeof(ff_byte) * 4), 1, file) != 1) {
+        return FF_RESULT_ERROR_READ_FILE_FAILURE;
+    }
+
+    // Get the big endian value of the length buffer
+    uint32_t data_chunk_length = get_big_endian(length_buffer);
+
+    // 2. Read type (ditto)
+    // (we are really just doing the same as before and we don't have to move any positions cause
+    //  thank god, FILE can already do that, *ascends*)
+    uint32_t type_buffer;
+
+    if (fread(&type_buffer, sizeof(sizeof(ff_byte) * 4), 1, file) != 1) {
+        return FF_RESULT_ERROR_READ_FILE_FAILURE;
+    }
+
+    // Get the big endian value of the type buffer
+    // It needs to be mapped to the enum though
+    uint32_t chunk_type = get_big_endian(type_buffer);
+
+    // 3. Read data (data_chunk_length bytes)
+    uint32_t *data_buffer = (uint32_t)malloc(data_chunk_length * sizeof(ff_byte));
+
+    if (fread(data_buffer, sizeof(ff_byte), data_chunk_length, file) != data_chunk_length) {
+        free(data_buffer);
+        return FF_RESULT_ERROR_READ_FILE_FAILURE;
+    }
+
+    // 4. Read CRC (4 bytes)
+    // However, I don't think we need to use the data right now
+    // so we can just read and store it
+    uint32_t crc_buffer;
+
+    if (fread(&crc_buffer, sizeof(sizeof(ff_byte) * 4), 1, file) != 1) {
+        free(data_buffer);
+        return FF_RESULT_ERROR_READ_FILE_FAILURE;
+    }
+
+    uint16_t crc = get_big_endian(crc_buffer);
+
+    // 5. Create a chunk struct and return it
+    ff_png_chunk *out = (ff_png_chunk *)malloc(sizeof(ff_png_chunk));
+    out->length = data_chunk_length;
+    out->type = chunk_type;
+    out->data = data_buffer;
+    out->crc = crc;
+    *out_chunk = out;
+
+    return FF_RESULT_OK;
 }
\ No newline at end of file
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