base64 encode in JS

1 files changed, 44 insertions, 0 deletions

diff --git a/src/gleam_stdlib.js b/src/gleam_stdlib.js
index 3658142..d26a4b6 100644
--- a/src/gleam_stdlib.js
+++ b/src/gleam_stdlib.js
@@ -382,3 +382,47 @@ export function parse_query(query) {
     return new Error(Nil);
   }
 }
+
+// From https://developer.mozilla.org/en-US/docs/Glossary/Base64#Solution_2_%E2%80%93_rewrite_the_DOMs_atob()_and_btoa()_using_JavaScript's_TypedArrays_and_UTF-8
+export function encode64(bit_string) {
+  let aBytes = bit_string.buffer;
+  let nMod3 = 2,
+    sB64Enc = "";
+
+  for (let nLen = aBytes.length, nUint24 = 0, nIdx = 0; nIdx < nLen; nIdx++) {
+    nMod3 = nIdx % 3;
+    if (nIdx > 0 && ((nIdx * 4) / 3) % 76 === 0) {
+      sB64Enc += "\r\n";
+    }
+    nUint24 |= aBytes[nIdx] << ((16 >>> nMod3) & 24);
+    if (nMod3 === 2 || aBytes.length - nIdx === 1) {
+      sB64Enc += String.fromCharCode(
+        uint6ToB64((nUint24 >>> 18) & 63),
+        uint6ToB64((nUint24 >>> 12) & 63),
+        uint6ToB64((nUint24 >>> 6) & 63),
+        uint6ToB64(nUint24 & 63)
+      );
+      nUint24 = 0;
+    }
+  }
+
+  return (
+    sB64Enc.substr(0, sB64Enc.length - 2 + nMod3) +
+    (nMod3 === 2 ? "" : nMod3 === 1 ? "=" : "==")
+  );
+}
+
+// From https://developer.mozilla.org/en-US/docs/Glossary/Base64#Solution_2_%E2%80%93_rewrite_the_DOMs_atob()_and_btoa()_using_JavaScript's_TypedArrays_and_UTF-8
+function uint6ToB64(nUint6) {
+  return nUint6 < 26
+    ? nUint6 + 65
+    : nUint6 < 52
+    ? nUint6 + 71
+    : nUint6 < 62
+    ? nUint6 - 4
+    : nUint6 === 62
+    ? 43
+    : nUint6 === 63
+    ? 47
+    : 65;
+}