refactor(workspace): split workspace interface and implementation (#5463)

@affine/workspace -> (@affine/workspace, @affine/workspace-impl)

packages/frontend/workspace-impl/src/utils/buffer-to-blob.ts

@@ -0,0 +1,59 @@
+import isSvg from 'is-svg';
+
+function fastCheckIsNotSvg(buffer: Uint8Array) {
+  // check first non-whitespace character is not '<svg' or '<?xml'
+  for (let i = 0; i < buffer.length; i++) {
+    const ch = buffer[i];
+
+    // skip whitespace
+    if (
+      ch === 0x20 /* \s */ ||
+      ch === 0x09 /* \t */ ||
+      ch === 0x0b /* \v */ ||
+      ch === 0x0c /* \f */ ||
+      ch === 0x0a /* \n */ ||
+      ch === 0x0d /* \r */ ||
+      ch === 0xa0
+    ) {
+      continue;
+    }
+
+    return (
+      !(
+        buffer[i] === /* '<' */ 0x3c &&
+        buffer[i + 1] === /* 's' */ 0x73 &&
+        buffer[i + 2] === /* 'v' */ 0x76 &&
+        buffer[i + 3] === /* 'g' */ 0x67
+      ) &&
+      !(
+        buffer[i] === /* '<' */ 0x3c &&
+        buffer[i + 1] === /* '?' */ 0x3f &&
+        buffer[i + 2] === /* 'x' */ 0x78 &&
+        buffer[i + 3] === /* 'm' */ 0x6d &&
+        buffer[i + 4] === /* 'l' */ 0x6c
+      )
+    );
+  }
+
+  return true;
+}
+
+// this has a overhead of converting to string for testing if it is svg.
+export function isSvgBuffer(buffer: Uint8Array) {
+  if (fastCheckIsNotSvg(buffer)) {
+    return false;
+  }
+  const decoder = new TextDecoder('utf-8');
+  const str = decoder.decode(buffer);
+  return isSvg(str);
+}
+
+export function bufferToBlob(buffer: Uint8Array | ArrayBuffer) {
+  const isSVG = isSvgBuffer(
+    buffer instanceof ArrayBuffer ? new Uint8Array(buffer) : buffer
+  );
+  // for svg blob, we need to explicitly set the type to image/svg+xml
+  return isSVG
+    ? new Blob([buffer], { type: 'image/svg+xml' })
+    : new Blob([buffer]);
+}