ObjectStorage

This is a library for working with object storage services, like Amazon AWS S3, Digital Ocean Spaces, or Minio. It is written in C and conforms to the ANSI C99 standard for maximum compatibility. It uses libCurl to handle making the HTTP requests and libCrypto from OpenSSL to handle the Sha256 hashing.

Usage

example.c contains a complete example of how to use the library, and buildExample.sh shows how to link in libCurl and libCrypto. The accessID and secret key are just to a test instance of Minio (https://minio.io/) and will have to be changed to your own accessID and secret key.

Types

struct ObjectStore {
    const char* host; 
    const char* secretKey;
    const char* accessID;
    const char* region;
    const char* bucketName;
};

ObjectStore is used to store all the information needed to connect to a particular bucket on a particular service.

For example, to initialize an ObjectStore for a bucket named "test" on S3 in the us-east-1 region:

    struct ObjectStore myStore;
    myStore.host = "s3.amazonaws.com";
    myStore.secretKey = "AWS4WhaterYourSecretKeyIs";
    myStore.accessID = "WhateverYourAccessIDIs";
    myStore.region = "us-east-1";
    myStore.bucketName = "test";

Note that the secret key must start with "AWS4", if your service does not show that, go ahead and add it.

Functions

The curl argument to each of these functions if used to make the HTTP request and can be left as NULL. For better performance though, an initialized instance should be passed in.

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Get An Object

char* getObjectFromBucket(struct ObjectStore store, const char* objName, int* resultLen, CURL* curl, enum ObjectStoreResult* result);

This function fetches the object with the name in objName from the given store and sets the length of the fetched data to resultLen and returns a pointer to the data. The status code is set to result and is OBJ_STORE_OK on success, OBJ_STORE_NOT_FOUND if the object does not exist, and OBJ_STORE_ERROR if some other error occurred.

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Upload Object

enum ObjectStoreResult uploadObjectToBucket(struct ObjectStore store, const char* data, int dataLen, const char* objName, CURL* curl);

This function uploads an object with the name in objName and contents stored in data with the length dataLen to the location specified by store. Returns OBJ_STORE_OK on success, and OBJ_STORE_ERROR on failure.

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Upload File

    enum ObjectStoreResult uploadFileToBucket(struct ObjectStore store, const char* file, CURL* curl);

Similar to uploading an object, but instead of passing in data, pass in a file path. The file at file is read and uploaded with the same file name. Returns OBJ_STORE_OK on success, and OBJ_STORE_ERROR on failure.

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Check If Object Exists

enum ObjectStoreResult doesObjectExistInBucket(struct ObjectStore store, const char* objName, CURL* curl);

This function checks if there is an object in the given store with the name in objName. Returns OBJ_STORE_EXISTS if found, OBJ_STORE_NOT_FOUND if not, and OBJ_STORE_ERROR if some error occurred.

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Delete An Object

enum ObjectStoreResult deleteObjectFromBucket(struct ObjectStore store, const char* objName, CURL* curl);

This function deletes an object with the name in objName from the given store. Returns OBJ_STORE_OK on success, OBJ_STORE_NOT_FOUND if the object does not exist, and OBJ_STORE_ERROR if some other error occurred.

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