Refactor reading the strip data fields into a function

src/tiff/tiffread.c

@@ -44,6 +44,15 @@ struct tiff_reader {
   Pixel *pixels;
 };
 
+typedef struct strip_data_field StripDataField;
+struct strip_data_field {
+  u32 *strip_value;
+  const ShortLongValue *value_from_file;
+  u32 strip_index;
+  u32 length_in_bytes;
+  u16 type_byte_count;
+};
+
 TiffHdr read_tiff_header(const TiffReader *reader);
 TiffIFD read_ifd(const TiffReader *reader, Arena *arena);
 TiffImage read_fields(const TiffReader *reader);
@@ -52,6 +61,7 @@ bool read_strip_data(TiffReader *reader, Arena *arena);
 void read_strips(const TiffReader *reader, Pixel *buf);
 bool read_field(const TiffField *field, TiffImage *img);
 bool validate_image_type(const TiffImage *img);
+void read_strip_data_field(const TiffReader *reader, StripDataField *field);
 void read_from_file_with_offset(FILE *fp, void *dst, u64 count, u64 offset);
 
 Image *read_baseline_tiff(const char *file, Arena *arena) {
@@ -282,32 +292,6 @@ LOAD_IMAGE_PIXELS_RETURN:
   return buf;
 }
 
-#if 0
-void read_strip_field(FILE *fp, const TiffHdr *header, const TiffImage *img, TiffStrip *strip) {
-  if (offsets_total_bytes > sizeof(u32)) {
-    u32 offset = img->strip_offsets.long_val + offset_size * i;
-    read_from_file_with_offset(fp, &(strip->offset), offset_size, offset);
-
-    switch (header->order) {
-    case TIFF_ORDER_BIG_ENDIAN:
-      if (IS_LITTLE_ENDIAN) {
-        strip->offset = offset_size > sizeof(u16) ? ntohl(strip->offset)
-                                                  : ntohs(strip->offset);
-      }
-      break;
-    case TIFF_ORDER_LITTLE_ENDIAN:
-      if (IS_BIG_ENDIAN) {
-        strip->offset = offset_size > sizeof(u16) ? htonl(strip->offset)
-                                                  : htons(strip->offset);
-      }
-      break;
-    }
-  } else {
-    memcpy(&(strip->offset), &(img->strip_offsets.long_val), offset_size);
-  }
-}
-#endif
-
 bool read_strip_data(TiffReader *reader, Arena *arena) {
   reader->img.strips =
       wapp_mem_arena_alloc(arena, sizeof(TiffStrip) * reader->img.strip_count);
@@ -332,59 +316,23 @@ bool read_strip_data(TiffReader *reader, Arena *arena) {
 
   for (u32 i = 0; i < reader->img.strip_count; ++i) {
     TiffStrip *strip = &(reader->img.strips[i]);
+    StripDataField offsets = {
+        .strip_value = &(strip->offset),
+        .value_from_file = &(reader->img.strip_offsets),
+        .strip_index = i,
+        .length_in_bytes = offsets_total_bytes,
+        .type_byte_count = offset_size,
+    };
+    StripDataField counts = {
+        .strip_value = &(strip->byte_count),
+        .value_from_file = &(reader->img.strip_byte_counts),
+        .strip_index = i,
+        .length_in_bytes = byte_count_total_bytes,
+        .type_byte_count = counts_size,
+    };
 
-    // read_strip_field(reader, &(strip->offset), &(reader->img.strip_offsets),
+    read_strip_data_field(reader, &offsets);
-    // i, offsets_total_bytes, offset_size);
+    read_strip_data_field(reader, &counts);
-
-    if (offsets_total_bytes > sizeof(u32)) {
-      u32 offset = reader->img.strip_offsets.long_val + offset_size * i;
-      read_from_file_with_offset(reader->fp, &(strip->offset), offset_size,
-                                 offset);
-
-      switch (reader->header.order) {
-      case TIFF_ORDER_BIG_ENDIAN:
-        if (IS_LITTLE_ENDIAN) {
-          strip->offset = offset_size > sizeof(u16) ? ntohl(strip->offset)
-                                                    : ntohs(strip->offset);
-        }
-        break;
-      case TIFF_ORDER_LITTLE_ENDIAN:
-        if (IS_BIG_ENDIAN) {
-          strip->offset = offset_size > sizeof(u16) ? htonl(strip->offset)
-                                                    : htons(strip->offset);
-        }
-        break;
-      }
-    } else {
-      memcpy(&(strip->offset), &(reader->img.strip_offsets.long_val),
-             offset_size);
-    }
-
-    if (byte_count_total_bytes > sizeof(u32)) {
-      u32 offset = reader->img.strip_byte_counts.long_val + counts_size * i;
-      read_from_file_with_offset(reader->fp, &(strip->byte_count), counts_size,
-                                 offset);
-
-      switch (reader->header.order) {
-      case TIFF_ORDER_BIG_ENDIAN:
-        if (IS_LITTLE_ENDIAN) {
-          strip->byte_count = counts_size > sizeof(u16)
-                                  ? ntohl(strip->byte_count)
-                                  : ntohs(strip->byte_count);
-        }
-        break;
-      case TIFF_ORDER_LITTLE_ENDIAN:
-        if (IS_BIG_ENDIAN) {
-          strip->byte_count = counts_size > sizeof(u16)
-                                  ? htonl(strip->byte_count)
-                                  : htons(strip->byte_count);
-        }
-        break;
-      }
-    } else {
-      memcpy(&(strip->byte_count), &(reader->img.strip_byte_counts.long_val),
-             counts_size);
-    }
   }
 
   return true;
@@ -582,6 +530,42 @@ bool validate_image_type(const TiffImage *img) {
   return true;
 }
 
+void read_strip_data_field(const TiffReader *reader, StripDataField *field) {
+  u16 tiff_long_byte_count = field_types[TIFF_FIELD_TYPE_LONG].byte_count;
+
+  bool value_is_file_offset = field->length_in_bytes > tiff_long_byte_count;
+  u32 offset = field->type_byte_count * field->strip_index;
+
+  if (!value_is_file_offset) {
+    u8 *value = (u8 *)&(field->value_from_file->long_val);
+    memcpy(field->strip_value, value + offset, field->type_byte_count);
+
+    return;
+  }
+
+  read_from_file_with_offset(reader->fp, field->strip_value,
+                             field->type_byte_count,
+                             field->value_from_file->long_val + offset);
+
+  u16 tiff_short_byte_count = field_types[TIFF_FIELD_TYPE_SHORT].byte_count;
+  switch (reader->header.order) {
+  case TIFF_ORDER_BIG_ENDIAN:
+    if (IS_LITTLE_ENDIAN) {
+      *(field->strip_value) = field->type_byte_count > tiff_short_byte_count
+                                  ? ntohl(*(field->strip_value))
+                                  : ntohs(*(field->strip_value));
+    }
+    break;
+  case TIFF_ORDER_LITTLE_ENDIAN:
+    if (IS_BIG_ENDIAN) {
+      *(field->strip_value) = field->type_byte_count > tiff_short_byte_count
+                                  ? htonl(*(field->strip_value))
+                                  : htons(*(field->strip_value));
+    }
+    break;
+  }
+}
+
 void read_from_file_with_offset(FILE *fp, void *dst, u64 count, u64 offset) {
   if (!fp || !dst) {
     return;