S3 的 C++ 接口实例

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2023-12-01

配置

下面的 includes 和 globals 将会在随后的例子中用到:

#include "libs3.h"
#include <stdlib.h>
#include <iostream>
#include <fstream>

const char access_key[] = "ACCESS_KEY";
const char secret_key[] = "SECRET_KEY";
const char host[] = "HOST";
const char sample_bucket[] = "sample_bucket";
const char sample_key[] = "hello.txt";
const char sample_file[] = "resource/hello.txt";

S3BucketContext bucketContext =
{
        host,
        sample_bucket,
        S3ProtocolHTTP,
        S3UriStylePath,
        access_key,
        secret_key
};

S3Status responsePropertiesCallback(
                const S3ResponseProperties *properties,
                void *callbackData)
{
        return S3StatusOK;
}

static void responseCompleteCallback(
                S3Status status,
                const S3ErrorDetails *error,
                void *callbackData)
{
        return;
}

S3ResponseHandler responseHandler =
{
        &responsePropertiesCallback,
        &responseCompleteCallback
};

新建 (和关闭) 一个连接

下面的代码将新建一个连接用来很服务器进行交互.

S3_initialize("s3", S3_INIT_ALL, host);
// Do stuff...
S3_deinitialize();

列出当前用户的所有 Bucket

下面的代码会列出你所有的 bucket 的列表。这也会打印出每个bucket的 bucket 名、所有者 ID 和显示名称

static S3Status listServiceCallback(
                const char *ownerId,
                const char *ownerDisplayName,
                const char *bucketName,
                int64_t creationDate, void *callbackData)
{
        bool *header_printed = (bool*) callbackData;
        if (!*header_printed) {
                *header_printed = true;
                printf("%-22s", "       Bucket");
                printf("  %-20s  %-12s", "     Owner ID", "Display Name");
                printf("\n");
                printf("----------------------");
                printf("  --------------------" "  ------------");
                printf("\n");
        }

        printf("%-22s", bucketName);
        printf("  %-20s  %-12s", ownerId ? ownerId : "", ownerDisplayName ? ownerDisplayName : "");
        printf("\n");

        return S3StatusOK;
}

S3ListServiceHandler listServiceHandler =
{
        responseHandler,
        &listServiceCallback
};
bool header_printed = false;
S3_list_service(S3ProtocolHTTP, access_key, secret_key, host, 0, &listServiceHandler, &header_printed);

新建一个 Bucket

这会新建一个 bucket。

S3_create_bucket(S3ProtocolHTTP, access_key, secret_key, host, sample_bucket, S3CannedAclPrivate, NULL, NULL, &responseHandler, NULL);

列出 Bucket 的内容

下面的代码会输出 bucket 内的所有对象列表。这也会打印出每一个对象的名字、文件尺寸和最近修改时间。

static S3Status listBucketCallback(
                int isTruncated,
                const char *nextMarker,
                int contentsCount,
                const S3ListBucketContent *contents,
                int commonPrefixesCount,
                const char **commonPrefixes,
                void *callbackData)
{
        printf("%-22s", "      Object Name");
        printf("  %-5s  %-20s", "Size", "   Last Modified");
        printf("\n");
        printf("----------------------");
        printf("  -----" "  --------------------");
        printf("\n");

    for (int i = 0; i < contentsCount; i++) {
        char timebuf[256];
                char sizebuf[16];
        const S3ListBucketContent *content = &(contents[i]);
                time_t t = (time_t) content->lastModified;

                strftime(timebuf, sizeof(timebuf), "%Y-%m-%dT%H:%M:%SZ", gmtime(&t));
                sprintf(sizebuf, "%5llu", (unsigned long long) content->size);
                printf("%-22s  %s  %s\n", content->key, sizebuf, timebuf);
    }

    return S3StatusOK;
}

S3ListBucketHandler listBucketHandler =
{
        responseHandler,
        &listBucketCallback
};
S3_list_bucket(&bucketContext, NULL, NULL, NULL, 0, NULL, &listBucketHandler, NULL);

输出形式类似下面这样:

myphoto1.jpg 251262  2011-08-08T21:35:48.000Z
myphoto2.jpg 262518  2011-08-08T21:38:01.000Z

删除一个 Bucket

Note

Bucket必须为空！否则它不会工作!

S3_delete_bucket(S3ProtocolHTTP, S3UriStylePath, access_key, secret_key, host, sample_bucket, NULL, &responseHandler, NULL);

新建一个对象 (来源于一个文件)

下面的代码会新建一个文件``hello.txt``.

#include <sys/stat.h>
typedef struct put_object_callback_data
{
    FILE *infile;
    uint64_t contentLength;
} put_object_callback_data;


static int putObjectDataCallback(int bufferSize, char *buffer, void *callbackData)
{
    put_object_callback_data *data = (put_object_callback_data *) callbackData;

    int ret = 0;

    if (data->contentLength) {
        int toRead = ((data->contentLength > (unsigned) bufferSize) ? (unsigned) bufferSize : data->contentLength);
                ret = fread(buffer, 1, toRead, data->infile);
    }
    data->contentLength -= ret;
    return ret;
}

put_object_callback_data data;
struct stat statbuf;
if (stat(sample_file, &statbuf) == -1) {
        fprintf(stderr, "\nERROR: Failed to stat file %s: ", sample_file);
        perror(0);
        exit(-1);
}

int contentLength = statbuf.st_size;
data.contentLength = contentLength;

if (!(data.infile = fopen(sample_file, "r"))) {
        fprintf(stderr, "\nERROR: Failed to open input file %s: ", sample_file);
        perror(0);
        exit(-1);
}

S3PutObjectHandler putObjectHandler =
{
        responseHandler,
        &putObjectDataCallback
};

S3_put_object(&bucketContext, sample_key, contentLength, NULL, NULL, &putObjectHandler, &data);

下载一个对象 (到文件)

下面的代码会下载一个文件并打印它的内容.

static S3Status getObjectDataCallback(int bufferSize, const char *buffer, void *callbackData)
{
        FILE *outfile = (FILE *) callbackData;
        size_t wrote = fwrite(buffer, 1, bufferSize, outfile);
        return ((wrote < (size_t) bufferSize) ? S3StatusAbortedByCallback : S3StatusOK);
}

S3GetObjectHandler getObjectHandler =
{
        responseHandler,
        &getObjectDataCallback
};
FILE *outfile = stdout;
S3_get_object(&bucketContext, sample_key, NULL, 0, 0, NULL, &getObjectHandler, outfile);

删除一个对象

下面的代码会删除一个对象.

S3ResponseHandler deleteResponseHandler =
{
        0,
        &responseCompleteCallback
};
S3_delete_object(&bucketContext, sample_key, 0, &deleteResponseHandler, 0);

改变一个对象的 ACL

下面的代码会改变一个对象的 ACL 来授权所有控制给另一个用户.

#include <string.h>
char ownerId[] = "owner";
char ownerDisplayName[] = "owner";
char granteeId[] = "grantee";
char granteeDisplayName[] = "grantee";

S3AclGrant grants[] = {
        {
                S3GranteeTypeCanonicalUser,
                {{}},
                S3PermissionFullControl
        },
        {
                S3GranteeTypeCanonicalUser,
                {{}},
                S3PermissionReadACP
        },
        {
                S3GranteeTypeAllUsers,
                {{}},
                S3PermissionRead
        }
};

strncpy(grants[0].grantee.canonicalUser.id, ownerId, S3_MAX_GRANTEE_USER_ID_SIZE);
strncpy(grants[0].grantee.canonicalUser.displayName, ownerDisplayName, S3_MAX_GRANTEE_DISPLAY_NAME_SIZE);

strncpy(grants[1].grantee.canonicalUser.id, granteeId, S3_MAX_GRANTEE_USER_ID_SIZE);
strncpy(grants[1].grantee.canonicalUser.displayName, granteeDisplayName, S3_MAX_GRANTEE_DISPLAY_NAME_SIZE);

S3_set_acl(&bucketContext, sample_key, ownerId, ownerDisplayName, 3, grants, 0, &responseHandler, 0);

生成对象下载 URL (带签名)

下面的代码会生成一个带签名的有效时间为5分钟的下载URL

#include <time.h>
char buffer[S3_MAX_AUTHENTICATED_QUERY_STRING_SIZE];
int64_t expires = time(NULL) + 60 * 5; // Current time + 5 minutes

S3_generate_authenticated_query_string(buffer, &bucketContext, sample_key, expires, NULL);