From 953af9e80e3b165eb99da90d6c64e79803a460c0 Mon Sep 17 00:00:00 2001
From: Loreto Parisi <loretoparisi@gmail.com>
Date: Fri, 20 Jul 2018 16:17:55 +0200
Subject: [PATCH] Added Chromaprint fingerprint comparation

---
 lib/compare.coffee | 72 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 lib/compare.coffee

diff --git a/lib/compare.coffee b/lib/compare.coffee
new file mode 100644
index 0000000..12b4bc0
--- /dev/null
+++ b/lib/compare.coffee
@@ -0,0 +1,72 @@
+#
+# Compare Two Chroma print Fingerprint
+# Inspired to Python Algorithm https://github.com/bjjb/chromaprint.js/issues/3
+# Other sources from here https://groups.google.com/forum/#!topic/acoustid/7AQk8XlycEk
+# @author Loreto Parisi (loretoparisi at gmail dot com) - JavaScript version
+#
+ord = (string) ->
+  #  discuss at: http://locutus.io/php/ord/
+  # original by: Kevin van Zonneveld (http://kvz.io)
+  # bugfixed by: Onno Marsman (https://twitter.com/onnomarsman)
+  # improved by: Brett Zamir (http://brett-zamir.me)
+  #    input by: incidence
+  #   example 1: ord('K')
+  #   returns 1: 75
+  #   example 2: ord('\uD800\uDC00'); // surrogate pair to create a single Unicode character
+  #   returns 2: 65536
+  str = string + ''
+  code = str.charCodeAt(0)
+  if code >= 0xD800 and code <= 0xDBFF
+    # High surrogate (could change last hex to 0xDB7F to treat
+    # high private surrogates as single characters)
+    hi = code
+    if str.length == 1
+      # This is just a high surrogate with no following low surrogate,
+      # so we return its value;
+      return code
+      # we could also throw an error as it is not a complete character,
+      # but someone may want to know
+    low = str.charCodeAt(1)
+    return (hi - 0xD800) * 0x400 + low - 0xDC00 + 0x10000
+  if code >= 0xDC00 and code <= 0xDFFF
+    # Low surrogate
+    # This is just a low surrogate with no preceding high surrogate,
+    # so we return its value;
+    return code
+    # we could also throw an error as it is not a complete character,
+    # but someone may want to know
+  code
+
+compare_b64_fingerprint = (a, b) ->
+  'returns inverse bit error rate in percent'
+  a = b64decode(a)
+  b = b64decode(b)
+  matching_bits = 0
+  different_bits = 0
+  if b.length != a.length
+    # trim to shortest
+    shortest = min(len(a), len(b))
+    longest = max(len(a), len(b))
+    a = a.slice(0, shortest)
+    b = b.slice(0, shortest)
+    # extra bits count as different
+    different_bits = 8 * (longest - shortest)
+  i = 0
+  while i < a.length
+    byte_a = ord(a.slice(i, i + 1))
+    byte_b = ord(b.slice(i, i + 1))
+    x = 0
+    while x < 8
+      bit_a = byte_a >> x & 1
+      bit_b = byte_b >> x & 1
+      if bit_a == bit_b
+        matching_bits += 1
+      else
+        different_bits += 1
+      x++
+    i++
+  total_bits = different_bits + matching_bits
+  float(matching_bits) / float(total_bits)
+
+# ---
+# generated by js2coffee 2.2.0
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