1 files changed, 24 insertions, 0 deletions
diff --git a/src/util.ts b/src/util.ts
new file mode 100644
index 0000000..9ef9797
--- /dev/null
+++ b/src/util.ts
@@ -0,0 +1,24 @@
+export class DataFormatError extends Error {};
+
+/*
+ * TODO: remove once node 24 is EOL (2028-05-01?)
+ * node <25 doesn't have Uint8Array.fromHex, so we use Buffer.from(_, "hex") instead
+ */
+type fromHex = (s: string) => Uint8Array | Buffer;
+const fromHex: fromHex = "fromHex" in Uint8Array
+  ? Uint8Array.fromHex as fromHex
+  : (s: string) => Buffer.from(s, "hex");
+
+export function loadHex(source: string, target: Uint8Array) {
+  for (const line of source.split('\n')) {
+    if (line[0] !== ":") continue;
+    if (line.length < 11) throw new DataFormatError("line too short");
+    const data = fromHex(line.slice(1).trimEnd());
+    if (data[3]) return new DataFormatError("unexpected data[3] !== 0");
+    const n = data[0];
+    const addr = (data[1] << 8) | data[2];
+    if (addr + n > target.length) new DataFormatError("target address out of bounds");
+    if (n + 4 !== data.length) new DataFormatError("inconsistent data length");
+    target.set(data.subarray(4), addr);
+  }
+}