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https://github.com/softmotions/aws4

AWS API client library in pure C
https://github.com/softmotions/aws4

amazon amazon-web-services aws aws-api aws-client aws-http-api aws-http-client aws-s3 aws-sdk aws-sdk-c aws-sdk-cpp c c-library client dynamodb

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AWS API client library in pure C

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# AWS API client library in pure C



AWS4 is a C client library used for signing and sending requests to AWS HTTP APIs (aws4.h).

Also it offers a simple DynamoDB client API (aws4dd.h) and **Distributed Resources Locking API (aws4dl.h)**.



Softmotions AWS4 library is very lightweight and It is not bloated with tons of dependencies.



## Prerequisites



* libcurl with SSL enabled

* gcc or clang C11 compiler (tested on clang v14 / gcc v11) 

* cmake v3.18+, make or ninja



## How to build



```sh

git clone https://github.com/Softmotions/aws4

cd ./aws4 && mkdir ./build

cmake -DCMAKE_BUILD_TYPE=Release  ..

make

```



## Usage



Look into `./src/aws4.h` and `./src/aws4dd.h` for API documentation.



Also look into test cases in `./src/tests` directory.



### Examples



#### DynamoDB API Put Item



```c

#include 



iwrc rc = 0;

struct aws4dd_item_put *op = 0;

struct aws4dd_response *resp = 0;



aws4dd_item_put_op(&op, &(struct aws4dd_item_put_spec) {

  .table_name = "Thread",

  .condition_expression = "ForumName <> :f and Subject <> :s"

});



aws4dd_item_put_value(op, "/ExpressionAttributeValues/:f", "S", "Amazon DynamoDB");

aws4dd_item_put_value(op, "/ExpressionAttributeValues/:s", "S", "How do I update multiple items?");



aws4dd_item_put_value(op, "/Item/LastPostDateTime", "S", "201303190422");

aws4dd_item_put_array(op, "/Item/Tags", "SS", (const char*[]) { "Update", "Multiple", "Help", 0 });

aws4dd_item_put_value(op, "/Item/ForumName", "S", "Amazon DynamoDB");

aws4dd_item_put_value(op, "/Item/Message", "S", "I want to update multiple items in a single call.");

aws4dd_item_put_value(op, "/Item/Subject", "S", "How do I update multiple items?");

aws4dd_item_put_value(op, "/Item/LastPostedBy", "S", "[email protected]");



aws4dd_item_put(&request_spec, op, &resp);



aws4dd_response_destroy(&resp);

aws4dd_item_put_op_destroy(&op);

return rc;

```



#### DynamoDB API Query



```c



RCC(rc, finish, aws4dd_query_op(&op, &(struct  aws4dd_query_spec) {

  .table_name = s->spec.service_table,

  .key_condition_expression = "kind = :kind",

  .filter_expression = "ttl <= :ttl",

  .projection_expression = "kind",

  .limit = 1,

  .consistent_read = true,

}));



RCC(rc, finish, aws4dd_query_value(op, "/ExpressionAttributeValues/:kind", "S", s->spec.kind));

RCC(rc, finish, aws4dd_query_value(op, "/ExpressionAttributeValues/:ttl", "N", ttl));

RCC(rc, finish, aws4dd_query(&s->spec.request_spec, op, &resp));



if (!jbn_at(resp->data, "/Items/0", &n) || n->type != JBV_OBJECT) {

  *out = false;

} else {

  *out = true;

}



...



```



#### Low level universal AWS4 API



```c

iwrc rc = 0;

char *out = 0;



rc = aws4_request_raw(&(struct aws4_request_spec) {

  .flags = AWS_SERVICE_DYNAMODB,

  .aws_region = "us-east-1",

  .aws_key = "fakeMyKeyId",

  .aws_secret_key = "fakeSecretAccessKey",

  .aws_url = "http://localhost:8000"

}, &(struct aws4_request_payload) {

  .payload = "{}",

  .payload_len = IW_LLEN("{}"),

  .amz_target = "DynamoDB_20120810.ListTables"

}, &out);



IWN_ASSERT(rc == 0);

IWN_ASSERT(out);



if (out) {

  IWN_ASSERT(0 == strcmp(out, "{\"TableNames\":[]}"))

}



free(out);

return rc;

```



#### Distributed Resources Locking API



```c

iwrc rc = 0;

struct aws4dl_lock *lock = 0;

struct aws4dl_lock_acquire_spec spec = {

  .request                  = request_spec,

  .poller                   = poller,

};



RCC(rc, finish, aws4dl_lock_acquire(&spec, &lock));



// Critical section...



RCC(rc, finish, aws4dl_lock_release(&lock));



finish:

if (rc) {

  iwlog_ecode_error3(rc);

}

return rc;

```



## Tips



To make AWS API calls more efficient you can use a global `aws4_request_spec` structure and 

specify globaly initialized `curl` handle in it. This will avoid creating a new `curl` handle

for each request. Note that you should not use a shared `curl` handle in a multi-threaded environment.



## IWSTART



[IWSTART](https://github.com/Softmotions/iwstart) is an automatic CMake initial project generator for C projects based on 

[iowow](https://github.com/Softmotions/iowow) / 

[iwnet](https://github.com/Softmotions/iwnet) / 

[ejdb2](https://github.com/Softmotions/ejdb) / 

[aws4](https://github.com/Softmotions/aws4) libs.

You may use it to create a new C project template from scratch based on thiese libs.



# License

```



MIT License



Copyright (c) 2012-2023 Softmotions Ltd 



Permission is hereby granted, free of charge, to any person obtaining a copy

of this software and associated documentation files (the "Software"), to deal

in the Software without restriction, including without limitation the rights

to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

copies of the Software, and to permit persons to whom the Software is

furnished to do so, subject to the following conditions:



The above copyright notice and this permission notice shall be included in all

copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

SOFTWARE.



```