flywithu/Learning-Bitcoin-from-the-Command-Line
1
1
Fork 0
mirror of https://github.com/ChristopherA/Learning-Bitcoin-from-the-Command-Line.git synced 2025-10-30 18:07:22 +00:00
Code Issues Releases Wiki Activity

Update 12_2_Accessing_Bitcoind_with_C.md

Browse Source
This commit is contained in:
Shannon Appelcline 2017-06-20 10:50:33 -07:00 committed by GitHub
parent 4f8f91e64e
commit a8ac096af4
1 changed files with 119 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

127
12_2_Accessing_Bitcoind_with_C.md
View File

@ -121,15 +121,19 @@ printf ("%s\n", json_dumps (jsonresult, JSON_INDENT(2)));
Alternatively, you can drill down to an individual item like `blocks`:
```
json_t *jsonblocks = NULL;
jsonresult = json_object_get(jsonresult,"blocks");
jsonblocks = json_object_get(jsonresult,"blocks");
int blocks;
blocks = json_integer_value(jsonresult);
blocks = json_integer_value(jsonblocks);
printf("Block Count: %d\n",blocks);
```
Appendix II has an example of this complete code, with the variable initiatialization all rearranged to the top, and with cleanup of the JSON objects.
Appendix II has an example of this complete code.
[[SUMMARY]]
## Summary: Accessing Bitcoind with C
By linking to the `bitcoinrpc` and `jansson` libraries, you can easily access `bitcoind` via RPC calls from a C library. To do so, you create an RPC connection, then make individual RPC calls. `jansson` then allows you to decode the JSON responses.
_What is the power of C?_ C allows you to take the next step beyond shell-scripting, permitting the creation of more comprehensive and robust programs. A more comprehensive example will appear in the next chapter.
## Appendix I: Testing a Bitcoind Connection
@ -169,8 +173,115 @@ Successfully connected to server!
```
## Appendix II: Getting Mining Info
[[APPENDIX 2: First Code]]
[[clean up organizing of initialization of variables]]
[[FREE up the JSON objects]]
Here's the complete code for the `getmininginfo` command, with organized variable initiatialization, error checking, and variable cleanup.
```
file: getmininginfo.c
[[BREAK OUT TWO MORE CHAPTERS ON GETTING INFO + PUTTING TRANSACTION TOGETHER; OR 1?]]
#include <jansson.h>
#include <bitcoinrpc.h>
int main(void) {
bitcoinrpc_cl_t *rpc_client;
bitcoinrpc_method_t *getmininginfo = NULL;
bitcoinrpc_resp_t *btcresponse = NULL;
bitcoinrpc_err_t btcerror;
json_t *jsonresponse = NULL;
json_t *jsonresult = NULL;
json_t *jsonblocks = NULL;
int blocks;
bitcoinrpc_global_init();
rpc_client = bitcoinrpc_cl_init_params ("bitcoinrpc", "73bd45ba60ab8f9ff9846b6404769487", "127.0.0.1", 18332);
if (rpc_client) {
getmininginfo = bitcoinrpc_method_init(BITCOINRPC_METHOD_GETMININGINFO);
if (!getmininginfo) {
printf("ERROR: Unable to initialize getmininginfo method!\n");
exit(-1);
}
btcresponse = bitcoinrpc_resp_init();
if (!btcresponse) {
printf("Error: Cannot initialize response object!\n");
exit(-1);
}
bitcoinrpc_call(rpc_client, getmininginfo, btcresponse, &btcerror);
if (btcerror.code != BITCOINRPCE_OK) {
printf("Error: getmininginfo error code %d [%s]\n", btcerror.code,btcerror.msg);
exit(-1);
}
printf("Full Response: ");
jsonresponse = bitcoinrpc_resp_get (btcresponse);
printf ("%s\n", json_dumps (jsonresponse, JSON_INDENT(2)));
printf("\nJust the Result: ");
jsonresult = json_object_get(jsonresponse,"result");
printf ("%s\n", json_dumps (jsonresult, JSON_INDENT(2)));
jsonblocks = json_object_get(jsonresult,"blocks");
blocks = json_integer_value(jsonblocks);
printf("\nBlock Count: %d\n",blocks);
json_decref(jsonblocks);
json_decref(jsonresult);
json_decref(jsonresponse);
} else {
printf("ERROR: Failed to connect to server!\n");
}
bitcoinrpc_cl_free(rpc_client);
bitcoinrpc_global_cleanup();
}
```
As usual, you can compile and run as follows:
```
$ cc getmininginfo.c -lbitcoinrpc -ljansson -o getmininginfo
$ ./getmininginfo
Full Response: {
"id": "03406237-cd8f-466d-ac31-86711ea9d1db",
"result": {
"blocks": 1147154,
"errors": "Warning: unknown new rules activated (versionbit 28)",
"pooledtx": 0,
"currentblocksize": 0,
"currentblockweight": 0,
"currentblocktx": 0,
"difficulty": 313525.08513550513,
"networkhashps": 3958339463617.417,
"chain": "test"
},
"error": null
}
Just the Result: {
"blocks": 1147154,
"errors": "Warning: unknown new rules activated (versionbit 28)",
"pooledtx": 0,
"currentblocksize": 0,
"currentblockweight": 0,
"currentblocktx": 0,
"difficulty": 313525.08513550513,
"networkhashps": 3958339463617.417,
"chain": "test"
}
Block Count: 1147154
```