Refactor C++ code

Split features into their own file

Style is becoming less C, more C++

src/common.cc

@@ -0,0 +1,99 @@
+#include <string>
+#include <string.h>
+#include <vips/vips.h>
+
+#include "common.h"
+
+// How many tasks are in the queue?
+volatile int counter_queue = 0;
+
+// How many tasks are being processed?
+volatile int counter_process = 0;
+
+// Filename extension checkers
+static bool ends_with(std::string const &str, std::string const &end) {
+  return str.length() >= end.length() && 0 == str.compare(str.length() - end.length(), end.length(), end);
+}
+bool is_jpeg(std::string const &str) {
+  return ends_with(str, ".jpg") || ends_with(str, ".jpeg") || ends_with(str, ".JPG") || ends_with(str, ".JPEG");
+}
+bool is_png(std::string const &str) {
+  return ends_with(str, ".png") || ends_with(str, ".PNG");
+}
+bool is_webp(std::string const &str) {
+  return ends_with(str, ".webp") || ends_with(str, ".WEBP");
+}
+bool is_tiff(std::string const &str) {
+  return ends_with(str, ".tif") || ends_with(str, ".tiff") || ends_with(str, ".TIF") || ends_with(str, ".TIFF");
+}
+
+unsigned char const MARKER_JPEG[] = {0xff, 0xd8};
+unsigned char const MARKER_PNG[] = {0x89, 0x50};
+unsigned char const MARKER_WEBP[] = {0x52, 0x49};
+
+/*
+  Initialise a VipsImage from a buffer. Supports JPEG, PNG and WebP.
+  Returns the ImageType detected, if any.
+*/
+ImageType
+sharp_init_image_from_buffer(VipsImage **image, void *buffer, size_t const length, VipsAccess const access) {
+  ImageType imageType = UNKNOWN;
+  if (memcmp(MARKER_JPEG, buffer, 2) == 0) {
+    if (!vips_jpegload_buffer(buffer, length, image, "access", access, NULL)) {
+      imageType = JPEG;
+    }
+  } else if(memcmp(MARKER_PNG, buffer, 2) == 0) {
+    if (!vips_pngload_buffer(buffer, length, image, "access", access, NULL)) {
+      imageType = PNG;
+    }
+  } else if(memcmp(MARKER_WEBP, buffer, 2) == 0) {
+    if (!vips_webpload_buffer(buffer, length, image, "access", access, NULL)) {
+      imageType = WEBP;
+    }
+  }
+  return imageType;
+}
+
+/*
+  Initialise a VipsImage from a file.
+  Returns the ImageType detected, if any.
+*/
+ImageType
+sharp_init_image_from_file(VipsImage **image, char const *file, VipsAccess const access) {
+  ImageType imageType = UNKNOWN;
+  if (vips_foreign_is_a("jpegload", file)) {
+    if (!vips_jpegload(file, image, "access", access, NULL)) {
+      imageType = JPEG;
+    }
+  } else if (vips_foreign_is_a("pngload", file)) {
+    if (!vips_pngload(file, image, "access", access, NULL)) {
+      imageType = PNG;
+    }
+  } else if (vips_foreign_is_a("webpload", file)) {
+    if (!vips_webpload(file, image, "access", access, NULL)) {
+      imageType = WEBP;
+    }
+  } else if (vips_foreign_is_a("tiffload", file)) {
+    if (!vips_tiffload(file, image, "access", access, NULL)) {
+      imageType = TIFF;
+    }
+  } else if(vips_foreign_is_a("magickload", file)) {
+    if (!vips_magickload(file, image, "access", access, NULL)) {
+      imageType = MAGICK;
+    }
+  }
+  return imageType;
+}
+
+/*
+  Does this image have an alpha channel?
+  Uses colour space interpretation with number of channels to guess this.
+*/
+bool
+sharp_image_has_alpha(VipsImage *image) {
+  return (
+    (image->Bands == 2 && image->Type == VIPS_INTERPRETATION_B_W) ||
+    (image->Bands == 4 && image->Type != VIPS_INTERPRETATION_CMYK) ||
+    (image->Bands == 5 && image->Type == VIPS_INTERPRETATION_CMYK)
+  );
+}