netcdf-c/libnczarr/zs3sdk.cpp
Dennis Heimbigner 6b69b9c52c Significantly Improve Amazon S3 Cloud Storage Support
## S3 Related Fixes

* Add comprehensive support for specifying AWS profiles to provide access credentials.
* Parse the files "~/.aws/config" and "~/.aws/credentials to provide credentials for the HDF5 ROS3 driver and to locate default region.
* Add a function to obtain the currently active S3 credentials. The search rules are defined in docs/nczarr.md.
* Provide documentation for the new features.
* Modify the struct NCauth (in include/ncauth.h) to replace specific S3 credentials with a profile name.
* Add a unit test to test the operation of profile and credentials management.
* Add support for URLS of the form "s3://<bucket>/<key>"; this requires obtaining a default region.
* Allows the specification of profile and/or region in a URL of the form "#mode=nczarr,...&aws.region=...&aws.profile=..."

## Misc. Fixes

* Move the ezxml code to libdispatch so that it can be used both by DAP4 and nczarr.
* Modify nclist to provide a deep clone operation.
* Modify ncuri to provide a deep clone operation.
* Modify the .rc file format to allow the specification of a path to be tested when looking for an entry in the .rc file.
* Ensure that the NC_rcload function is called.
* Modify nchttp to support setting request headers.
2021-09-27 18:36:33 -06:00

693 lines
21 KiB
C++

/*
* Copyright 2018, University Corporation for Atmospheric Research
* See netcdf/COPYRIGHT file for copying and redistribution conditions.
*/
#define NOOP
#include "awsincludes.h"
#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <streambuf>
#include "netcdf.h"
#include "zincludes.h"
#include "zs3sdk.h"
#ifdef __CYGWIN__
extern char* strdup(const char*);
#endif
#define size64_t unsigned long long
static Aws::SDKOptions zs3options;
/* Forward */
static Aws::S3::Model::BucketLocationConstraint s3findregion(const char* name);
static int s3objectinfo1(const Aws::S3::Model::Object& s3_object, char** fullkeyp, size64_t* lenp);
static int s3objectsinfo(Aws::Vector<Aws::S3::Model::Object> list, size_t*, char*** keysp, size64_t** lenp);
static int s3commonprefixes(Aws::Vector<Aws::S3::Model::CommonPrefix> list, char*** keysp);
static void freestringenvv(char** ss);
static int makes3key(const char* pathkey, const char** keyp);
static int makes3keydir(const char* prefix, char** prefixdirp);
static char** mergekeysets(size_t nkeys1, char** keys1, size_t nkeys2, char** keys2);
static const char*
dumps3info(ZS3INFO* info)
{
static char text[8192];
snprintf(text,sizeof(text),"host=%s region=%s bucket=%s rootkey=%s profile=%s",
(info->host?info->host:"null"),
(info->region?info->region:"null"),
(info->bucket?info->bucket:"null"),
(info->rootkey?info->rootkey:"null"),
(info->profile?info->profile:"null"));
return text;
}
void
NCZ_s3sdkinitialize(void)
{
ZTRACE(11,NULL);
Aws::InitAPI(zs3options);
ZUNTRACE(NC_NOERR);
}
void
NCZ_s3sdkfinalize(void)
{
ZTRACE(11,NULL);
Aws::ShutdownAPI(zs3options);
ZUNTRACE(NC_NOERR);
}
static char*
makeerrmsg(const Aws::Client::AWSError<Aws::S3::S3Errors> err, const char* key="")
{
char* errmsg;
size_t len;
len = strlen(err.GetExceptionName().c_str()) + strlen(err.GetMessage().c_str()) + strlen(key) + 10;
if((errmsg = (char*)malloc(len+1))==NULL)
return NULL;
snprintf(errmsg,len,"%s %s key=%s",
err.GetExceptionName().c_str(),
err.GetMessage().c_str(),
key);
return errmsg;
}
static Aws::Client::ClientConfiguration*
s3sdkcreateconfig(ZS3INFO* info)
{
int stat = NC_NOERR;
ZTRACE(11,"info=%s", dumps3info(info));
Aws::Client::ClientConfiguration *config;
if(info->profile)
config = new Aws::Client::ClientConfiguration(info->profile);
else
config = new Aws::Client::ClientConfiguration();
config->scheme = Aws::Http::Scheme::HTTPS;
config->connectTimeoutMs = 300000;
config->requestTimeoutMs = 600000;
if(info->region) config->region = info->region;
if(info->host) config->endpointOverride = info->host;
config->enableEndpointDiscovery = true;
config->followRedirects = Aws::Client::FollowRedirectsPolicy::ALWAYS;
ZUNTRACE(NC_NOERR);
return config;
}
void*
NCZ_s3sdkcreateclient(ZS3INFO* info)
{
ZTRACE(11,NULL);
Aws::Client::ClientConfiguration* config = s3sdkcreateconfig(info);
Aws::S3::S3Client *s3client;
if(info->profile == NULL || strcmp(info->profile,"none")==0) {
Aws::Auth::AWSCredentials creds;
creds.SetAWSAccessKeyId(Aws::String(""));
creds.SetAWSSecretKey(Aws::String(""));
s3client = new Aws::S3::S3Client(creds,*config,
Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy::RequestDependent,
false);
} else {
s3client = new Aws::S3::S3Client(*config,
Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy::RequestDependent,
false);
}
delete config;
ZUNTRACE(NC_NOERR);
return (void*)s3client;
}
int
NCZ_s3sdkbucketexists(void* s3client0, const char* bucket, int* existsp, char** errmsgp)
{
int stat = NC_NOERR;
int exists = 0;
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
ZTRACE(11,"bucket=%s",bucket);
if(errmsgp) *errmsgp = NULL;
auto result = s3client->ListBuckets();
if(!result.IsSuccess()) {
if(errmsgp) *errmsgp = makeerrmsg(result.GetError());
stat = NC_ES3;
} else {
Aws::Vector<Aws::S3::Model::Bucket> bucket_list = result.GetResult().GetBuckets();
for(auto const &awsbucket : bucket_list) {
auto name = awsbucket.GetName();
if(name == bucket) {exists = 1; break;}
}
}
if(existsp) *existsp = exists;
return ZUNTRACEX(stat,"exists=%d",*existsp);
}
int
NCZ_s3sdkbucketcreate(void* s3client0, const char* region, const char* bucket, char** errmsgp)
{
int stat = NC_NOERR;
ZTRACE(11,"region=%s bucket=%s",region,bucket);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
if(errmsgp) *errmsgp = NULL;
const Aws::S3::Model::BucketLocationConstraint &awsregion = s3findregion(region);
if(awsregion == Aws::S3::Model::BucketLocationConstraint::NOT_SET)
return NC_EURL;
/* Set up the request */
Aws::S3::Model::CreateBucketRequest create_request;
create_request.SetBucket(bucket);
if(region) {
/* Specify the region as a location constraint */
Aws::S3::Model::CreateBucketConfiguration bucket_config;
bucket_config.SetLocationConstraint(awsregion);
create_request.SetCreateBucketConfiguration(bucket_config);
}
#ifdef NOOP
/* Create the bucket */
auto create_result = s3client->CreateBucket(create_request);
if(!create_result.IsSuccess()) {
if(errmsgp) *errmsgp = makeerrmsg(create_result.GetError());
stat = NC_ES3;;
}
#else
fprintf(stderr,"create bucket: %s\n",bucket); fflush(stderr);
#endif
return ZUNTRACE(stat);
}
int
NCZ_s3sdkbucketdelete(void* s3client0, ZS3INFO* info, char** errmsgp)
{
int stat = NC_NOERR;
ZTRACE(11,"info=%s%s",dumps3info(info));
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
if(errmsgp) *errmsgp = NULL;
const Aws::S3::Model::BucketLocationConstraint &awsregion = s3findregion(info->region);
if(awsregion == Aws::S3::Model::BucketLocationConstraint::NOT_SET)
return NC_EURL;
/* Set up the request */
Aws::S3::Model::DeleteBucketRequest request;
request.SetBucket(info->bucket);
#ifdef NOOP
/* Delete the bucket */
auto result = s3client->DeleteBucket(request);
if(!result.IsSuccess()) {
if(errmsgp) *errmsgp = makeerrmsg(result.GetError());
stat = NC_ES3;;
}
#else
fprintf(stderr,"delete bucket: %s\n",bucket); fflush(stderr);
#endif
return ZUNTRACE(stat);
}
/**************************************************/
/* Object API */
/*
@return NC_NOERR if key points to a content-bearing object.
@return NC_EEMPTY if object at key has no content.
@return NC_EXXX return true error
*/
int
NCZ_s3sdkinfo(void* s3client0, const char* bucket, const char* pathkey, size64_t* lenp, char** errmsgp)
{
int stat = NC_NOERR;
const char* key = NULL;
ZTRACE(11,"bucket=%s pathkey=%s",bucket,pathkey);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
Aws::S3::Model::HeadObjectRequest head_request;
if(*pathkey != '/') return NC_EINTERNAL;
/* extract the true s3 key*/
if((stat = makes3key(pathkey,&key))) return ZUNTRACE(stat);
if(errmsgp) *errmsgp = NULL;
head_request.SetBucket(bucket);
head_request.SetKey(key);
auto head_outcome = s3client->HeadObject(head_request);
if(head_outcome.IsSuccess()) {
long long l = head_outcome.GetResult().GetContentLength();
if(lenp) *lenp = (size64_t)l;
} else {
if(lenp) *lenp = 0;
/* Distinquish not-found from other errors */
switch (head_outcome.GetError().GetErrorType()) {
case Aws::S3::S3Errors::RESOURCE_NOT_FOUND:
stat = NC_EEMPTY;
break;
case Aws::S3::S3Errors::ACCESS_DENIED:
stat = NC_EACCESS;
/* fall thru */
default:
if(!stat) stat = NC_ES3;
if(errmsgp) *errmsgp = makeerrmsg(head_outcome.GetError(),key);
break;
}
}
return ZUNTRACEX(stat,"len=%d",(int)(lenp?*lenp:-1));
}
/*
@return NC_NOERR if success
@return NC_EXXX if fail
*/
int
NCZ_s3sdkread(void* s3client0, const char* bucket, const char* pathkey, size64_t start, size64_t count, void* content, char** errmsgp)
{
int stat = NC_NOERR;
char range[1024];
const char* key = NULL;
size64_t rangeend;
ZTRACE(11,"bucket=%s pathkey=%s start=%llu count=%llu content=%p",bucket,pathkey,start,count,content);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
Aws::S3::Model::GetObjectRequest object_request;
if(count == 0) return ZUNTRACE(stat);
if(*pathkey != '/') return NC_EINTERNAL;
if((stat = makes3key(pathkey,&key))) return ZUNTRACE(stat);
object_request.SetBucket(bucket);
object_request.SetKey(key);
rangeend = (start+count)-1;
snprintf(range,sizeof(range),"bytes=%llu-%llu",start,rangeend);
object_request.SetRange(range);
auto get_object_result = s3client->GetObject(object_request);
if(!get_object_result.IsSuccess()) {
if(errmsgp) *errmsgp = makeerrmsg(get_object_result.GetError(),key);
stat = NC_ES3;
} else {
/* Get the whole result */
Aws::IOStream &result = get_object_result.GetResultWithOwnership().GetBody();
std::string str((std::istreambuf_iterator<char>(result)),std::istreambuf_iterator<char>());
/* Verify actual result size */
size_t slen = str.size();
if(slen > count) return NC_ES3;
const char* s = str.c_str();
if(content)
memcpy(content,s,slen);
}
return ZUNTRACE(stat);
}
/*
For S3, I can see no way to do a byterange write;
so we are effectively writing the whole object
*/
int
NCZ_s3sdkwriteobject(void* s3client0, const char* bucket, const char* pathkey, size64_t count, const void* content, char** errmsgp)
{
int stat = NC_NOERR;
const char* key = NULL;
ZTRACE(11,"bucket=%s pathkey=%s count=%lld content=%p",bucket,pathkey,count,content);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
Aws::S3::Model::PutObjectRequest put_request;
if(*pathkey != '/') return ZUNTRACE(NC_EINTERNAL);
if((stat = makes3key(pathkey,&key))) return ZUNTRACE(stat);
if(errmsgp) *errmsgp = NULL;
put_request.SetBucket(bucket);
put_request.SetKey(key);
put_request.SetContentLength((long long)count);
std::shared_ptr<Aws::IOStream> data = std::shared_ptr<Aws::IOStream>(new Aws::StringStream());
data->rdbuf()->pubsetbuf((char*)content,count);
put_request.SetBody(data);
auto put_result = s3client->PutObject(put_request);
if(!put_result.IsSuccess()) {
if(errmsgp) *errmsgp = makeerrmsg(put_result.GetError(),key);
stat = NC_ES3;
}
return ZUNTRACE(stat);
}
int
NCZ_s3sdkclose(void* s3client0, ZS3INFO* info, int deleteit, char** errmsgp)
{
int stat = NC_NOERR;
ZTRACE(11,"info=%s rootkey=%s deleteit=%d",dumps3info(info),deleteit);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
if(deleteit) {
/* Delete the root key; ok it if does not exist */
switch (stat = NCZ_s3sdkdeletekey(s3client0,info->bucket,info->rootkey,errmsgp)) {
case NC_NOERR: break;
case NC_EEMPTY: case NC_ENOTFOUND: stat = NC_NOERR; break;
default: break;
}
}
delete s3client;
return ZUNTRACE(stat);
}
/*
Return a list of names of legal objects immediately below a specified key.
In theory, the returned list should be sorted in lexical order,
but it possible that it is not.
*/
int
NCZ_s3sdkgetkeys(void* s3client0, const char* bucket, const char* prefixkey0, size_t* nkeysp, char*** keysp, char** errmsgp)
{
int stat = NC_NOERR;
size_t nkeys = 0;
const char* prefix = NULL;
char* prefixdir = NULL;
char** realkeys = NULL;
char** commonkeys = NULL;
char** allkeys = NULL;
ZTRACE(11,"bucket=%s prefixkey0=%s",bucket,prefixkey0);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
Aws::S3::Model::ListObjectsV2Request objects_request;
if(*prefixkey0 != '/') return ZUNTRACE(NC_EINTERNAL);
/* Make sure that the prefix ends with '/' */
if((stat = makes3keydir(prefixkey0,&prefixdir))) return ZUNTRACE(stat);
/* remove leading '/' */
if((stat = makes3key(prefixdir,&prefix))) return ZUNTRACE(stat);
if(errmsgp) *errmsgp = NULL;
objects_request.SetBucket(bucket);
objects_request.SetPrefix(prefix);
objects_request.SetDelimiter("/"); /* Force return of common prefixes */
auto objects_outcome = s3client->ListObjectsV2(objects_request);
if(objects_outcome.IsSuccess()) {
size_t nrealkeys = 0;
size_t ncommonkeys = 0;
Aws::Vector<Aws::S3::Model::Object> object_list =
objects_outcome.GetResult().GetContents();
nrealkeys = (size_t)object_list.size();
stat = s3objectsinfo(object_list,NULL,&realkeys,NULL);
/* Add common prefixes */
Aws::Vector<Aws::S3::Model::CommonPrefix> common_list =
objects_outcome.GetResult().GetCommonPrefixes();
ncommonkeys = (size_t)common_list.size();
stat = s3commonprefixes(common_list,&commonkeys);
/* merge the two lists */
if((allkeys=mergekeysets(nrealkeys, realkeys, ncommonkeys, commonkeys))==NULL)
stat = NC_ENOMEM;
if(stat == NC_NOERR) {
if(nkeysp) {*nkeysp = nrealkeys + ncommonkeys;}
if(keysp) {*keysp = allkeys; allkeys = NULL;}
}
freestringenvv(allkeys);
freestringenvv(realkeys);
freestringenvv(commonkeys);
} else {
if(errmsgp) *errmsgp = makeerrmsg(objects_outcome.GetError());
stat = NC_ES3;
}
if(prefixdir) free(prefixdir);
return ZUNTRACEX(stat,"nkeys=%u",(unsigned)*nkeysp);
}
/*
Return a list of full keys of legal objects immediately below a specified key.
Not necessarily sorted.
*/
int
NCZ_s3sdksearch(void* s3client0, const char* bucket, const char* prefixkey0, size_t* nkeysp, char*** keysp, char** errmsgp)
{
int stat = NC_NOERR;
size_t nkeys = 0;
const char* prefix = NULL;
char* prefixdir = NULL;
char** keys = NULL;
ZTRACE(11,"bucket=%s prefixkey0=%s",bucket,prefixkey0);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
Aws::S3::Model::ListObjectsV2Request objects_request;
if(*prefixkey0 != '/') return ZUNTRACE(NC_EINTERNAL);
/* Make sure that the prefix ends with '/' */
if((stat = makes3keydir(prefixkey0,&prefixdir))) return ZUNTRACE(stat);
/* remove leading '/' */
if((stat = makes3key(prefixdir,&prefix))) return ZUNTRACE(stat);
if(errmsgp) *errmsgp = NULL;
objects_request.SetBucket(bucket);
objects_request.SetPrefix(prefix);
/* Do not use delimiter so we get all full key paths */
auto objects_outcome = s3client->ListObjectsV2(objects_request);
if(objects_outcome.IsSuccess()) {
size_t nkeys = 0;
Aws::Vector<Aws::S3::Model::Object> object_list =
objects_outcome.GetResult().GetContents();
nkeys = (size_t)object_list.size();
if((keys=(char**)calloc(sizeof(char*),(nkeys+1)))==NULL) /* NULL terminate list */
stat = NC_ENOMEM;
if(!stat) {
int i;
i = 0;
for (auto const &s3obj : object_list) {
const char* s;
const Aws::String& name = s3obj.GetKey();
s = name.c_str();
if(s != NULL) {
char* p;
size_t slen = name.length();
p = (char*)malloc(slen+1+1); /* nul plus leading '/' */
if(s[0] != '/') {p[0] = '/'; memcpy(p+1,s,slen); slen++;} else {memcpy(p,s,slen);}
p[slen] = '\0';
keys[i++] = p;
}
}
}
if(stat == NC_NOERR) {
if(nkeysp) {*nkeysp = nkeys;}
if(keysp) {*keysp = keys; keys = NULL;}
}
freestringenvv(keys);
} else {
if(errmsgp) *errmsgp = makeerrmsg(objects_outcome.GetError());
stat = NC_ES3;
}
if(prefixdir) free(prefixdir);
return ZUNTRACEX(stat,"nkeys=%u",(unsigned)*nkeysp);
}
int
NCZ_s3sdkdeletekey(void* s3client0, const char* bucket, const char* pathkey, char** errmsgp)
{
int stat = NC_NOERR;
const char* key = NULL;
ZTRACE(11,"bucket=%s pathkey=%s",bucket,pathkey);
Aws::S3::S3Client* s3client = (Aws::S3::S3Client*)s3client0;
Aws::S3::Model::DeleteObjectRequest delete_request;
if(*pathkey != '/') return NC_EINTERNAL;
if((stat = makes3key(pathkey,&key))) return ZUNTRACE(stat);
/* Delete this key object */
delete_request.SetBucket(bucket);
delete_request.SetKey(key);
auto delete_result = s3client->DeleteObject(delete_request);
if(!delete_result.IsSuccess()) {
if(errmsgp) *errmsgp = makeerrmsg(delete_result.GetError(),key);
stat = NC_ES3;
}
return ZUNTRACE(stat);
}
/*
Get Info about a single object from a vector
*/
static int
s3objectinfo1(const Aws::S3::Model::Object& s3_object, char** fullkeyp, size64_t* lenp)
{
int stat = NC_NOERR;
char* cstr = NULL;
if(fullkeyp) {
const char* key = NULL;
char* cstr = NULL;
auto s = s3_object.GetKey();
key = s.c_str();
if(key[0] == '/') {
cstr = strdup(key);
} else {
size_t len = strlen(key);
cstr = (char*)malloc(len+1+1);
if(cstr != NULL) {
cstr[0] = '/';
memcpy((void*)(cstr+1),(void*)key,len);
cstr[len+1] = '\0';
}
}
if(cstr == NULL) {
stat = NC_ENOMEM;
} else if(fullkeyp) {
*fullkeyp = cstr;
cstr = NULL;
}
}
if(!stat) {
if(lenp) *lenp = (size64_t)s3_object.GetSize();
}
if(cstr) free(cstr);
return stat;
}
/*
Get Info about a vector of objects; Keys are fixed up to start with a '/'
*/
static int
s3objectsinfo(Aws::Vector<Aws::S3::Model::Object> list, size_t* nkeysp, char*** keysp, size64_t** lenp)
{
int stat = NC_NOERR;
char** keys = NULL;
size_t nkeys;
size64_t *lengths = NULL;
int i;
nkeys = list.size();
if(nkeysp) *nkeysp = nkeys;
if((keys=(char**)calloc(sizeof(char*),(nkeys+1)))==NULL)
stat = NC_ENOMEM;
if(!stat) {
if((lengths=(size64_t*)calloc(sizeof(size64_t),(nkeys)))==NULL)
stat = NC_ENOMEM;
}
if(!stat) {
i = 0;
for (auto const &s3_object : list) {
stat = s3objectinfo1(s3_object,&keys[i],&lengths[i]);
i++;
if(stat) break;
}
}
if(!stat) {
if(keysp) {keys[nkeys] = NULL; *keysp = keys; keys = NULL;}
if(lenp) {*lenp = lengths; lengths = NULL;}
}
if(keys != NULL) freestringenvv(keys);
if(lengths != NULL) free(lengths);
return stat;
}
static int
s3commonprefixes(Aws::Vector<Aws::S3::Model::CommonPrefix> list, char*** keysp)
{
int stat = NC_NOERR;
char** keys = NULL;
size_t nkeys;
int i;
nkeys = list.size();
if((keys=(char**)calloc(sizeof(char*),(nkeys+1)))==NULL)
stat = NC_ENOMEM;
if(!stat) {
i = 0;
for (auto const &s3prefix : list) {
char* p; char* p1;
size_t len;
const Aws::String& prefix = s3prefix.GetPrefix();
len = prefix.length();
if((p = (char*) malloc(len+1+1))==NULL) /* for nul + leading '/' */
stat = NC_ENOMEM;
if(stat == NC_NOERR) {
if(*p == '/') {p1 = p;} else {*p = '/'; p1 = p+1;}
memcpy(p1,prefix.c_str(),len);
p1[len] = '\0';
keys[i++] = p;
}
}
}
if(keysp) {keys[nkeys] = NULL; *keysp = keys; keys = NULL;}
if(keys != NULL) freestringenvv(keys);
return stat;
}
static Aws::S3::Model::BucketLocationConstraint
s3findregion(const char* name)
{
return Aws::S3::Model::BucketLocationConstraintMapper::GetBucketLocationConstraintForName(name);
}
struct MemBuf: std::streambuf {
MemBuf(char* base, size_t size) {
char* p(base);
this->setg(p, p, p + size);
}
};
static void
freestringenvv(char** ss)
{
char** p;
if(ss != NULL) {
for(p=ss;*p;p++)
if(*p) free(*p);
free(ss);
}
}
static int
makes3key(const char* pathkey, const char** keyp)
{
assert(pathkey != NULL && pathkey[0] == '/');
if(keyp) *keyp = pathkey+1;
return NC_NOERR;
}
static int
makes3keydir(const char* prefix, char** prefixdirp)
{
size_t plen = strlen(prefix);
char* prefixdir = (char*)malloc(plen+1+1); /* '/' + nul */
if(prefixdir == NULL) return NC_ENOMEM;
memcpy(prefixdir,prefix,plen);
if(prefixdir[plen-1] != '/') {
prefixdir[plen++] = '/';
}
prefixdir[plen] = '\0';
*prefixdirp = prefixdir; prefixdir = NULL;
return NC_NOERR;
}
static char**
mergekeysets(size_t nkeys1, char** keys1, size_t nkeys2, char** keys2)
{
char** merge = NULL;
char** p1;
char** p2;
merge = (char**)malloc(sizeof(char*)*(nkeys1+nkeys2+1));
if(merge == NULL) return NULL;
if(nkeys1 > 0) {
memcpy(merge,keys1,sizeof(char*)*nkeys1);
/* avoid double free */
memset(keys1,0,sizeof(char*)*nkeys1);
}
if(nkeys2 > 0) {
memcpy(merge+nkeys1,keys2,sizeof(char*)*nkeys2);
/* avoid double free */
memset(keys2,0,sizeof(char*)*nkeys2);
}
merge[nkeys1+nkeys2] = NULL;
return merge;
}