get block height helper

1 files changed, 35 insertions, 0 deletions

diff --git a/lib/utils.js b/lib/utils.js
index 004ca7ac..1ff24c67 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -55,3 +55,38 @@ export const fail = msg => {
 
 export const SATS = 100000000;
 export const toSats = n => Math.round(n * SATS);
+
+export const getBlockHeight = message => {
+  let buffer = Buffer.from(message, "hex");
+  if (buffer.length < 80) throw new Error("Buffer too small (< 80 bytes)");
+
+  let offset = 0;
+  const readSlice = n => {
+    offset += n;
+    return buffer.slice(offset - n, offset);
+  };
+
+  const readUInt32 = () => {
+    const i = buffer.readUInt32LE(offset);
+    offset += 4;
+    return i;
+  };
+
+  const readUInt8 = () => {
+    const i = buffer.readUInt8(offset);
+    offset += 1;
+    return i;
+  };
+
+  const readVarInt = () => {
+    const vi = varuint.decode(buffer, offset);
+    offset += varuint.decode.bytes;
+    return vi;
+  };
+
+  readUInt32();
+  readSlice(32);
+  readSlice(32);
+  readUInt32();
+  return readUInt32();
+};