Add SVG stream parser

lib/parse_stream/svg.js

@@ -0,0 +1,186 @@
+'use strict';
+
+/* eslint-disable consistent-return */
+
+var once      = require('../common').once;
+var Transform = require('readable-stream').Transform;
+
+var STATE_IDENTIFY  = 0; // look for '<'
+var STATE_PARSE     = 1; // extract width and height from svg tag
+var STATE_IGNORE    = 2; // we got all the data we want, skip the rest
+
+// max size for pre-svg-tag comments plus svg tag itself
+var MAX_DATA_LENGTH = 65536;
+
+var SVG_HEADER_RE  = /<svg\s[^>]+>/;
+var SVG_WIDTH_RE   = /\bwidth="([^%]+?)"|\bwidth='([^%]+?)'/;
+var SVG_HEIGHT_RE  = /\bheight="([^%]+?)"|\bheight='([^%]+?)'/;
+var SVG_VIEWBOX_RE = /\bviewbox="(.+?)"|\bviewbox='(.+?)'/;
+var SVG_UNITS_RE   = /in$|mm$|cm$|pt$|pc$|px$|em$|ex$/;
+
+
+function isWhiteSpace(chr) {
+  return chr === 0x20 || chr === 0x09 || chr === 0x0D || chr === 0x0A;
+}
+
+
+function svgAttrs(str) {
+  var width   = str.match(SVG_WIDTH_RE);
+  var height  = str.match(SVG_HEIGHT_RE);
+  var viewbox = str.match(SVG_VIEWBOX_RE);
+
+  return {
+    width:   width && (width[1] || width[2]),
+    height:  height && (height[1] || height[2]),
+    viewbox: viewbox && (viewbox[1] || viewbox[2])
+  };
+}
+
+
+function units(str) {
+  if (!SVG_UNITS_RE.test(str)) return 'px';
+
+  return str.match(SVG_UNITS_RE)[0];
+}
+
+
+function parseSvg(str) {
+  if (!SVG_HEADER_RE.test(str)) return;
+
+  var attrs  = svgAttrs(str.match(SVG_HEADER_RE)[0]);
+  var width  = parseFloat(attrs.width) || 0;  // NaN -> 0
+  var height = parseFloat(attrs.height) || 0; // NaN -> 0
+
+  // Extract from direct values
+
+  if (attrs.width && attrs.height) {
+    if (width <= 0 || height <= 0) return;
+
+    return {
+      width:  width,
+      height: height,
+      type:   'svg',
+      mime:   'image/svg+xml',
+      wUnits: units(attrs.width),
+      hUnits: units(attrs.height)
+    };
+  }
+
+  // Extract from viewbox
+
+  var parts = (attrs.viewbox || '').split(' ');
+  var viewbox = {
+    width:  parts[2],
+    height: parts[3]
+  };
+  var vbWidth  = parseFloat(viewbox.width) || 0;  // NaN -> 0
+  var vbHeight = parseFloat(viewbox.height) || 0; // NaN -> 0
+
+  if (vbWidth <= 0 || vbHeight <= 0) return;
+  if (units(viewbox.width) !== units(viewbox.height)) return;
+
+  var ratio = vbWidth / vbHeight;
+
+  if (attrs.width) {
+    if (width <= 0) return;
+
+    return {
+      width:  width,
+      height: width / ratio,
+      type:   'svg',
+      mime:   'image/svg+xml',
+      wUnits: units(attrs.width),
+      hUnits: units(attrs.width)
+    };
+  }
+
+  if (attrs.height) {
+    if (height <= 0) return;
+
+    return {
+      width:  height * ratio,
+      height: height,
+      type:   'svg',
+      mime:   'image/svg+xml',
+      wUnits: units(attrs.height),
+      hUnits: units(attrs.height)
+    };
+  }
+
+  return {
+    width:  vbWidth,
+    height: vbHeight,
+    type:   'svg',
+    mime:   'image/svg+xml',
+    wUnits: units(viewbox.width),
+    hUnits: units(viewbox.height)
+  };
+}
+
+
+module.exports = function (input, _callback) {
+  var callback = once(_callback);
+  var state    = STATE_IDENTIFY;
+  var data_len = 0;
+  var str      = '';
+
+  var parser = new Transform({
+    transform: function transform(chunk, encoding, next) {
+      switch (state) {
+        case STATE_IDENTIFY:
+          var i = 0, max = chunk.length;
+
+          while (i < max && isWhiteSpace(chunk[i])) i++;
+
+          if (i >= max) {
+            data_len += chunk.length;
+
+            if (data_len > MAX_DATA_LENGTH) {
+              state = STATE_IGNORE;
+              callback();
+            }
+
+          } else if (chunk[i] === 0x3c /* < */) {
+            state = STATE_PARSE;
+            return transform(chunk, encoding, next);
+
+          } else {
+            state = STATE_IGNORE;
+            callback();
+          }
+
+          break;
+
+        case STATE_PARSE:
+          str += chunk.toString();
+
+          var result = parseSvg(str);
+
+          if (result) {
+            callback(null, result);
+            break;
+          }
+
+          data_len += chunk.length;
+
+          if (data_len > MAX_DATA_LENGTH) {
+            state = STATE_IGNORE;
+            callback();
+          }
+
+          break;
+      }
+
+      next();
+    },
+
+    flush: function () {
+      state = STATE_IGNORE;
+      callback();
+    }
+  });
+
+  input.pipe(parser);
+
+  return parser;
+};

lib/parse_sync/svg.js

@@ -2,10 +2,15 @@
 
 /* eslint-disable consistent-return */
 
+function isWhiteSpace(chr) {
+  return chr === 0x20 || chr === 0x09 || chr === 0x0D || chr === 0x0A;
+}
+
+
 function canBeSvg(buf) {
   var i = 0, max = buf.length;
 
-  while (i < max && buf[i] === 0x20) i++;
+  while (i < max && isWhiteSpace(buf[i])) i++;
 
   if (i === max) return false;
   return buf[i] === 0x3c; /* < */
@@ -72,7 +77,7 @@ module.exports = function (data) {
 
   // Extract from viewbox
 
-  var parts = attrs.viewbox.split(' ');
+  var parts = (attrs.viewbox || '').split(' ');
   var viewbox = {
     width:  parts[2],
     height: parts[3]

lib/parsers_stream.js

@@ -7,6 +7,7 @@ module.exports = {
   jpeg: require('./parse_stream/jpeg'),
   png:  require('./parse_stream/png'),
   psd:  require('./parse_stream/psd'),
+  svg:  require('./parse_stream/svg'),
   tiff: require('./parse_stream/tiff'),
   webp: require('./parse_stream/webp')
 };