Description
Collects all chunks from a file stream into memory, returning the complete content along with metadata. This is a convenience utility that uses streamFile internally.
Function Signature
async function collectFile(
stream: ReadableStream<Uint8Array>
): Promise<{ content: string | Uint8Array; metadata: FileMetadata }>
Parameters
stream
ReadableStream<Uint8Array>
required
The ReadableStream obtained from sandbox.readFileStream(path)
Returns
Object containing the complete file content and metadataComplete file content
string - For text files (all chunks concatenated)Uint8Array - For binary files (all chunks combined)
Metadata about the fileMIME type of the file (e.g., ‘image/png’, ‘text/plain’)
Whether the file is detected as binary
Encoding used for the file content
Examples
Read a text file
import { collectFile } from '@cloudflare/sandbox';
const stream = await sandbox.readFileStream('/workspace/config.json');
const { content, metadata } = await collectFile(stream);
if (typeof content === 'string') {
const config = JSON.parse(content);
console.log('Config:', config);
}
console.log('MIME type:', metadata.mimeType);
console.log('Size:', metadata.size, 'bytes');
Read a binary file
import { collectFile } from '@cloudflare/sandbox';
const stream = await sandbox.readFileStream('/workspace/image.png');
const { content, metadata } = await collectFile(stream);
if (content instanceof Uint8Array) {
console.log(`Read ${content.length} bytes`);
console.log('MIME type:', metadata.mimeType);
// Convert to base64 for transmission
const base64 = btoa(String.fromCharCode(...content));
return Response.json({ image: base64 });
}
Read and process markdown
import { collectFile } from '@cloudflare/sandbox';
const stream = await sandbox.readFileStream('/workspace/README.md');
const { content, metadata } = await collectFile(stream);
if (typeof content === 'string') {
const lines = content.split('\n');
const headers = lines.filter(line => line.startsWith('#'));
console.log('Headers found:', headers);
}
Read with type checking
import { collectFile } from '@cloudflare/sandbox';
const stream = await sandbox.readFileStream('/workspace/data.csv');
const { content, metadata } = await collectFile(stream);
if (metadata.isBinary) {
console.error('Expected text file, got binary');
return;
}
if (typeof content === 'string') {
const rows = content.split('\n').map(line => line.split(','));
console.log(`Parsed ${rows.length} rows`);
}
Download file from sandbox
import { collectFile } from '@cloudflare/sandbox';
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const sandbox = getSandbox(env.Sandbox, 'my-sandbox');
const stream = await sandbox.readFileStream('/workspace/report.pdf');
const { content, metadata } = await collectFile(stream);
return new Response(content, {
headers: {
'Content-Type': metadata.mimeType,
'Content-Length': metadata.size.toString(),
'Content-Disposition': 'attachment; filename="report.pdf"'
}
});
}
};
Compare with direct read
// Using collectFile (streaming approach)
import { collectFile } from '@cloudflare/sandbox';
const stream = await sandbox.readFileStream('/workspace/file.txt');
const { content } = await collectFile(stream);
// Using readFile (direct approach)
const result = await sandbox.readFile('/workspace/file.txt');
const content2 = result.content;
// Both give same result, but collectFile is better for large files
Error Handling
The function throws an error if:
- The file cannot be read
- The stream is interrupted
- Metadata is missing or invalid
import { collectFile } from '@cloudflare/sandbox';
try {
const stream = await sandbox.readFileStream('/workspace/file.txt');
const { content } = await collectFile(stream);
} catch (error) {
console.error('Failed to collect file:', error.message);
}
Notes
- Loads the entire file into memory - use
streamFile() for large files that need chunk processing
- Automatically handles text vs binary files
- Binary files are decoded from base64 automatically
- Simpler API than
streamFile() when you need the complete file
| Method | Memory Usage | Best For |
|---|
readFile() | Moderate | Small to medium files, simple use cases |
streamFile() | Low | Large files, chunk-by-chunk processing |
collectFile() | High | Any file size, when you need complete content |
See Also