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.
- libcurl with SSL enabled
- gcc or clang C11 compiler (tested on clang v14 / gcc v11)
- cmake v3.18+, make or ninja
git clone https://github.com/Softmotions/aws4
cd ./aws4 && mkdir ./build
cmake -DCMAKE_BUILD_TYPE=Release ..
make
Look into ./src/aws4.h
and ./src/aws4dd.h
for API documentation.
Also look into test cases in ./src/tests
directory.
#include <aws4/aws4dd.h>
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", "fred@example.com");
aws4dd_item_put(&request_spec, op, &resp);
aws4dd_response_destroy(&resp);
aws4dd_item_put_op_destroy(&op);
return rc;
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;
}
...
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;
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;
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 is an automatic CMake initial project generator for C projects based on iowow / iwnet / ejdb2 / aws4 libs. You may use it to create a new C project template from scratch based on thiese libs.
MIT License
Copyright (c) 2012-2023 Softmotions Ltd <info@softmotions.com>
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SOFTWARE.