Read each strip in a separate thread

src/tiff/tiffread.c

@@ -4,8 +4,10 @@
 #include "image.h"
 #include "mem_arena.h"
 #include <assert.h>
+#include <bits/pthreadtypes.h>
 #include <math.h>
 #include <netinet/in.h>
+#include <pthread.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -200,6 +202,7 @@ struct tiff_image {
 
 typedef struct tiff_reader TiffReader;
 struct tiff_reader {
+  const char *filename;
   FILE *fp;
   TiffHdr header;
   TiffIFD ifd;
@@ -214,7 +217,8 @@ internal void read_alpha(TiffReader *reader);
 internal void read_bits_per_sample(TiffReader *reader);
 internal bool read_image_pixels(TiffReader *reader, Arena *arena);
 internal bool read_strip_data(TiffReader *reader, Arena *arena);
-internal void read_strips(TiffReader *reader);
+internal bool read_strips(TiffReader *reader);
+internal void *read_strip(void *arg);
 internal void read_strip_data_field(const TiffReader *reader,
                                     StripDataField *field);
 internal bool read_field(const TiffField *field, TiffImage *img);
@@ -231,7 +235,7 @@ Image *read_baseline_tiff(const char *file, Arena *arena) {
     goto READ_BASELINE_RETURN_IMG;
   }
 
-  TiffReader reader = {.fp = fopen(file, "rb")};
+  TiffReader reader = {.filename = file, .fp = fopen(file, "rb")};
   if (!reader.fp) {
     goto READ_BASELINE_RETURN_IMG;
   }
@@ -534,9 +538,7 @@ internal bool read_image_pixels(TiffReader *reader, Arena *arena) {
     return false;
   }
 
-  read_strips(reader);
-
-  return true;
+  return read_strips(reader);
 }
 
 internal bool read_strip_data(TiffReader *reader, Arena *arena) {
@@ -585,42 +587,149 @@ internal bool read_strip_data(TiffReader *reader, Arena *arena) {
   return true;
 }
 
-internal void read_strips(TiffReader *reader) {
-  u64 position = 0;
-  u64 main_samples = reader->img.sample_count - reader->img.extra_samples_count;
-  TiffAlpha alpha = reader->img.alpha;
+// internal void read_strips(TiffReader *reader) {
+//   u64 position = 0;
+//   u64 main_samples = reader->img.sample_count -
+//   reader->img.extra_samples_count; TiffAlpha alpha = reader->img.alpha;
 
-  Pixel *p;
-  u64 start_offset;
-  u64 alpha_offset;
+//   Pixel *p;
+//   u64 start_offset;
+//   u64 alpha_offset;
+
+//   for (u64 i = 0; i < reader->img.strip_count; ++i) {
+//     const TiffStrip *strip = &(reader->img.strips[i]);
+
+//     for (u64 j = 0; j < strip->byte_count / reader->img.sample_count; ++j) {
+//       p = &(reader->pixels[position]);
+//       start_offset = strip->offset + j * reader->img.sample_count;
+//       alpha_offset = start_offset + main_samples + alpha.sample_offset;
+
+//       fread_with_offset(reader->fp, p, main_samples, start_offset);
+
+//       if (alpha.type == ALPHA_TYPE_UNDEFINED) {
+//         p->a = 255;
+//       } else {
+//         fread_with_offset(reader->fp, &(p->a), 1, alpha_offset);
+
+//         if (alpha.type == ALPHA_TYPE_UNASSOCIATED) {
+//           f32 a_norm = u8_normalise(p->a);
+
+//           p->r = u8_denormalise(u8_normalise(p->r) * a_norm);
+//           p->g = u8_denormalise(u8_normalise(p->g) * a_norm);
+//           p->b = u8_denormalise(u8_normalise(p->b) * a_norm);
+//         }
+//       }
+
+//       ++position;
+//     }
+//   }
+// }
+
+typedef struct strip_reader_args StripReaderArgs;
+struct strip_reader_args {
+  FILE *fp;
+  const TiffStrip *strip;
+  u64 pixel_count;
+  u64 samples_per_pixel;
+  u64 main_samples;
+  TiffAlpha alpha;
+  Pixel *pixel_write_start;
+};
+
+internal bool read_strips(TiffReader *reader) {
+  bool output = true;
+
+  u64 position = 0;
+  u64 strips_read = 0;
+  u64 threads_created = 0;
+  StripReaderArgs args[reader->img.strip_count];
+  pthread_t threads[reader->img.strip_count];
 
   for (u64 i = 0; i < reader->img.strip_count; ++i) {
     const TiffStrip *strip = &(reader->img.strips[i]);
+    u64 pixel_count = strip->byte_count / reader->img.sample_count;
+    args[i] = (StripReaderArgs){
+        .fp = fopen(reader->filename, "rb"),
+        .strip = strip,
+        .pixel_count = pixel_count,
+        .samples_per_pixel = reader->img.sample_count,
+        .main_samples =
+            reader->img.sample_count - reader->img.extra_samples_count,
+        .alpha = reader->img.alpha,
+        .pixel_write_start = &(reader->pixels[position]),
+    };
 
-    for (u64 j = 0; j < strip->byte_count / reader->img.sample_count; ++j) {
-      p = &(reader->pixels[position]);
-      start_offset = strip->offset + j * reader->img.sample_count;
-      alpha_offset = start_offset + main_samples + alpha.sample_offset;
-
-      fread_with_offset(reader->fp, p, main_samples, start_offset);
-
-      if (alpha.type == ALPHA_TYPE_UNDEFINED) {
-        p->a = 255;
-      } else {
-        fread_with_offset(reader->fp, &(p->a), 1, alpha_offset);
-
-        if (alpha.type == ALPHA_TYPE_UNASSOCIATED) {
-          f32 a_norm = u8_normalise(p->a);
-
-          p->r = u8_denormalise(u8_normalise(p->r) * a_norm);
-          p->g = u8_denormalise(u8_normalise(p->g) * a_norm);
-          p->b = u8_denormalise(u8_normalise(p->b) * a_norm);
-        }
-      }
-
-      ++position;
+    if (!args[i].fp) {
+      output = false;
+      goto READ_STRIPS_CLOSE_FILES;
     }
+
+    position += pixel_count;
+    ++strips_read;
   }
+
+  for (u64 i = 0; i < reader->img.strip_count; ++i) {
+    if (pthread_create(&(threads[i]), NULL, read_strip, (void *)&(args[i])) !=
+        0) {
+      break;
+    }
+
+    ++threads_created;
+  }
+
+  if (threads_created < reader->img.strip_count) {
+    for (u64 i = 0; i < strips_read; ++i) {
+      pthread_cancel(threads[i]);
+    }
+
+    return false;
+  }
+
+  for (u64 i = 0; i < reader->img.strip_count; ++i) {
+    pthread_join(threads[i], NULL);
+  }
+
+READ_STRIPS_CLOSE_FILES:
+  for (u64 i = 0; i < strips_read; ++i) {
+    fclose(args[i].fp);
+  }
+
+  return output;
+}
+
+internal void *read_strip(void *arg) {
+  StripReaderArgs *args = (StripReaderArgs *)arg;
+
+  Pixel *p;
+  u64 write_offset = 0;
+  u64 read_offset;
+  u64 alpha_offset;
+
+  for (u64 j = 0; j < args->pixel_count; ++j) {
+    p = args->pixel_write_start + write_offset;
+    read_offset = args->strip->offset + j * args->samples_per_pixel;
+    alpha_offset = read_offset + args->main_samples + args->alpha.sample_offset;
+
+    fread_with_offset(args->fp, p, args->main_samples, read_offset);
+
+    if (args->alpha.type == ALPHA_TYPE_UNDEFINED) {
+      p->a = 255;
+    } else {
+      fread_with_offset(args->fp, &(p->a), 1, alpha_offset);
+
+      if (args->alpha.type == ALPHA_TYPE_UNASSOCIATED) {
+        f32 a_norm = u8_normalise(p->a);
+
+        p->r = u8_denormalise(u8_normalise(p->r) * a_norm);
+        p->g = u8_denormalise(u8_normalise(p->g) * a_norm);
+        p->b = u8_denormalise(u8_normalise(p->b) * a_norm);
+      }
+    }
+
+    ++write_offset;
+  }
+
+  return NULL;
 }
 
 internal void read_strip_data_field(const TiffReader *reader,