s3cpp

Warning

WIP Currently supports only ListObjectsV2

A lightweight C++ client library for AWS S3, with zero 3rd party C++ dependencies (only libcurl and OpenSSL). Inspired by the AWS SDK for Go.

Architecture

Each S3 Client is organized onto modular components:

• src/s3cpp/httpclient: HTTP/1.1 client built on libCurl
• src/s3cpp/auth: AWS Signature V4 auth protocol (SigV4a pending)
• src/s3cpp/xml: A custom FSM for parsing XML

Basic Usage

#include <s3cpp/s3.h>

int main() {
    S3Client client("minio_access", "minio_secret");
    
    // List 100 objects with a prefix
    auto result = client.ListObjects("my-bucket", "path/to/", 100);
    
    if (!result) {
        std::println("Error: {}", result.error().Message);
        return 1;
    }
    
    for (const auto& obj : result->Contents) {
        std::println("Key: {}, Size: {}", obj.Key, obj.Size);
    }
    return 0;
}

For buckets with many objects, use the paginator to automatically handle continuation tokens:

#include <s3cpp/s3.h>

int main() {
    S3Client client("minio_access", "minio_secret");
    ListObjectsPaginator paginator(client, "my-bucket", "path/to/", 100);

    int totalObjects = 0;

    while (paginator.HasMorePages()) {
        std::expected<ListBucketResult, Error> page = paginator.NextPage();

				if (!page) {
            std::println("Error: {}", page.error().Message);
            return 1;
        }

        totalObjects += page->KeyCount;

        for (const auto& obj : page->Contents) {
            std::println("Key: {}", obj.Key);
        }
    }
    return 0;
}

Checking if a bucket exists:

#include <s3cpp/s3.h>

bool BucketExists(S3Client& client, const std::string& bucketName) {
    auto result = client.ListObjects(bucketName, "", 1);
    
    if (!result) {
        // Check the Resource Error field
        if (result.error().Resource == "/Does-not-exist") {
            return false;
        }
        // Other errors
        std::println("Error checking bucket: {}", result.error().Message);
        return false;
    }
    
    return true;
}

int main() {
    S3Client client("minio_access", "minio_secret");
    
    if (BucketExists(client, "my-bucket")) {
        std::println("Bucket exists");
    } else {
        std::println("Bucket does not exist");
    }
    
    return 0;
}

Build and Test

cmake -B build -DCMAKE_BUILD_TYPE=Debug
cmake --build build
./build/tests

Some tests require a local MinIO container to be running:

docker run -p 9000:9000 -p 9001:9001 \
  -e "MINIO_ROOT_USER=minio_access" \
  -e "MINIO_ROOT_PASSWORD=minio_secret" \
  quay.io/minio/minio server /data --console-address ":9001"

The test suite contains 37 tests covering HTTP, AWS SigV4, XML, and S3 ListObjectsV2