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mirror of https://github.com/rclone/rclone synced 2024-12-25 17:03:45 +01:00

librclone: exports, errors, docs and examples #4891

- rename C exports to be namespaced with Rclone prefix
- fix error handling in RcloneRPC
- add more examples
- add more docs
- add README
- simplify ctest Makefile
This commit is contained in:
Nick Craig-Wood 2021-02-26 10:41:38 +00:00
parent 316e65589b
commit 5db88fed2b
4 changed files with 140 additions and 62 deletions

31
librclone/README.md Normal file
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@ -0,0 +1,31 @@
# librclone
This directory contains code to build rclone as a C library and the
shims for accessing rclone from C.
The shims are a thin wrapper over the rclone RPC.
Build a shared library like this:
go build --buildmode=c-shared -o librclone.so github.com/rclone/rclone/librclone
Build a static library like this:
go build --buildmode=c-archive -o librclone.a github.com/rclone/rclone/librclone
Both the above commands will also generate `librclone.h` which should
be `#include`d in `C` programs wishing to use the library.
The library will depend on `libdl` and `libpthread`.
## Documentation
For documentation see the Go documentation for:
- [RcloneInitialize](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneInitialize)
- [RcloneFinalize](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneFinalize)
- [RcloneRPC](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneRPC)
## C Example
There is an example program `ctest.c` with Makefile in the `ctest` subdirectory

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@ -1,21 +1,13 @@
CFLAGS = -g -Wall
LDFLAGS = -L. -lrclone -lpthread -ldl
static: ctest
shared:
go build --buildmode=c-shared -o librclone.so github.com/rclone/rclone/librclone
ctest: ctest.o librclone.h
ctest: ctest.o librclone.a
$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
ctest.o: ctest.c librclone.h
$(CC) $(CFLAGS) -c $^ $(LDFLAGS)
build:
go build
librclone.h:
librclone.a librclone.h:
go build --buildmode=c-archive -o librclone.a github.com/rclone/rclone/librclone
clean:

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@ -4,29 +4,60 @@
#include <dlfcn.h>
#include "librclone.h"
// copy file using "operations/copyfile" command
void testCopyFile() {
struct CRPC_return res = CRPC("operations/copyfile", "{ \"srcFs\": \"/tmp\", \"srcRemote\": \"tmpfile\", \"dstFs\": \"/tmp\", \"dstRemote\": \"tmpfile2\" }");
printf("%d\n", res.r1); // status
printf("%s\n", res.r0); // output
free(res.r0);
void testRPC(char *method, char *in) {
struct RcloneRPC_return out = RcloneRPC(method, in);
printf("status: %d\n", out.r1);
printf("output: %s\n", out.r0);
free(out.r0);
}
// noop command
void testNoOp() {
struct CRPC_return res = CRPC("rc/noop", "{ \"p1\": [1,\"2\",null,4], \"p2\": { \"a\":1, \"b\":2 } }");
printf("%d\n", res.r1); // status
printf("%s\n", res.r0); // output
free(res.r0);
printf("test rc/noop\n");
testRPC("rc/noop",
"{"
" \"p1\": [1,\"2\",null,4],"
" \"p2\": { \"a\":1, \"b\":2 } "
"}");
}
// error command
void testError() {
printf("test rc/error\n");
testRPC("rc/error",
"{"
" \"p1\": [1,\"2\",null,4],"
" \"p2\": { \"a\":1, \"b\":2 } "
"}");
}
// copy file using "operations/copyfile" command
void testCopyFile() {
printf("test operations/copyfile\n");
testRPC("operations/copyfile",
"{"
"\"srcFs\": \"/tmp\","
"\"srcRemote\": \"tmpfile\","
"\"dstFs\": \"/tmp\","
"\"dstRemote\": \"tmpfile2\""
"}");
}
// list the remotes
void testListRemotes() {
printf("test operations/listremotes\n");
testRPC("config/listremotes", "{}");
}
int main(int argc, char** argv) {
printf("c main begin\n");
Cinit();
RcloneInitialize();
//testNoOp();
testNoOp();
testError();
testCopyFile();
testListRemotes();
Cdestroy();
RcloneFinalize();
return EXIT_SUCCESS;
}

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@ -1,13 +1,30 @@
// Package exports exports function for c library
// Package librclone exports shims for C library use
//
// This directory contains code to build rclone as a C library and the
// shims for accessing rclone from C.
//
// The shims are a thin wrapper over the rclone RPC.
//
// Build a shared library like this:
//
// go build --buildmode=c-shared -o librclone.so github.com/rclone/rclone/librclone
//
// Build a static library like this:
//
// go build --buildmode=c-archive -o librclone.a github.com/rclone/rclone/librclone
//
// Both the above commands will also generate `librclone.h` which should
// be `#include`d in `C` programs wishing to use the library.
//
// The library will depend on `libdl` and `libpthread`.
package main
import (
"C"
"bytes"
"context"
"encoding/json"
"io"
"fmt"
"net/http"
"runtime"
"strings"
@ -18,40 +35,51 @@ import (
"github.com/rclone/rclone/fs/rc/jobs"
_ "github.com/rclone/rclone/backend/all" // import all backends
_ "github.com/rclone/rclone/cmd/all" // import all commands
_ "github.com/rclone/rclone/lib/plugin" // import plugins
)
func init() {
// do nothing
}
// call to init the library
//export Cinit
func Cinit() {
// RcloneInitialize initializes rclone as a library
//
//export RcloneInitialize
func RcloneInitialize() {
// TODO: what need to be initialized manually?
}
// call to destroy the whole thing
//export Cdestroy
func Cdestroy() {
// RcloneFinalize finalizes the library
//
//export RcloneFinalize
func RcloneFinalize() {
// TODO: how to clean up? what happens when rcserver terminates?
// what about unfinished async jobs?
runtime.GC()
}
// RcloneRPC does a single RPC call. The inputs are (method, input)
// and the output is (output, status). This is an exported interface
// to the rclone API as described in https://rclone.org/rc/
//
// method is a string, eg "operations/list"
// input should be a serialized JSON object
// output will be returned as a serialized JSON object
// status is a HTTP status return (200=OK anything else fail)
//
// Caller is responsible for freeing the memory for output
// TODO: how to specify config file?
//export CRPC
func CRPC(method *C.char, input *C.char) (output *C.char, status C.int) {
//
// Note that when calling from C output and status are returned in an
// RcloneRPC_return which has two members r0 which is output and r1
// which is status.
//
//export RcloneRPC
func RcloneRPC(method *C.char, input *C.char) (output *C.char, status C.int) { //nolint:golint
res, s := callFunctionJSON(C.GoString(method), C.GoString(input))
return C.CString(res), C.int(s)
}
// copied from rcserver.go
// writeError writes a formatted error to the output
func writeError(path string, in rc.Params, w io.Writer, err error, status int) {
// writeError returns a formatted error string and the status passed in
func writeError(path string, in rc.Params, err error, status int) (string, int) {
fs.Errorf(nil, "rc: %q: error: %v", path, err)
var w strings.Builder
// FIXME should factor this
// Adjust the error return for some well known errors
errOrig := errors.Cause(err)
switch {
@ -61,7 +89,7 @@ func writeError(path string, in rc.Params, w io.Writer, err error, status int) {
status = http.StatusBadRequest
}
// w.WriteHeader(status)
err = rc.WriteJSON(w, rc.Params{
err = rc.WriteJSON(&w, rc.Params{
"status": status,
"error": err.Error(),
"input": in,
@ -69,8 +97,9 @@ func writeError(path string, in rc.Params, w io.Writer, err error, status int) {
})
if err != nil {
// can't return the error at this point
fs.Errorf(nil, "rc: failed to write JSON output: %v", err)
return fmt.Sprintf(`{"error": "rc: failed to write JSON output: %v"}`, err), status
}
return w.String(), status
}
// operations/uploadfile and core/command are not supported as they need request or response object
@ -78,32 +107,27 @@ func writeError(path string, in rc.Params, w io.Writer, err error, status int) {
// call a rc function using JSON to input parameters and output the resulted JSON
func callFunctionJSON(method string, input string) (output string, status int) {
// create a buffer to capture the output
buf := new(bytes.Buffer)
in := make(rc.Params)
err := json.NewDecoder(strings.NewReader(input)).Decode(&in)
if err != nil {
// TODO: handle error
writeError(method, in, buf, errors.Wrap(err, "failed to read input JSON"), http.StatusBadRequest)
return buf.String(), http.StatusBadRequest
return writeError(method, in, errors.Wrap(err, "failed to read input JSON"), http.StatusBadRequest)
}
// Find the call
call := rc.Calls.Get(method)
if call == nil {
writeError(method, in, buf, errors.Errorf("couldn't find method %q", method), http.StatusNotFound)
return buf.String(), http.StatusNotFound
return writeError(method, in, errors.Errorf("couldn't find method %q", method), http.StatusNotFound)
}
// TODO: handle these cases
if call.NeedsRequest {
writeError(method, in, buf, errors.Errorf("method %q needs request, not supported", method), http.StatusNotFound)
return buf.String(), http.StatusNotFound
return writeError(method, in, errors.Errorf("method %q needs request, not supported", method), http.StatusNotFound)
// Add the request to RC
//in["_request"] = r
}
if call.NeedsResponse {
writeError(method, in, buf, errors.Errorf("method %q need response, not supported", method), http.StatusNotFound)
return buf.String(), http.StatusNotFound
return writeError(method, in, errors.Errorf("method %q need response, not supported", method), http.StatusNotFound)
//in["_response"] = w
}
@ -112,22 +136,22 @@ func callFunctionJSON(method string, input string) (output string, status int) {
_, out, err := jobs.NewJob(context.Background(), call.Fn, in)
if err != nil {
// handle error
writeError(method, in, buf, err, http.StatusInternalServerError)
return buf.String(), http.StatusInternalServerError
return writeError(method, in, err, http.StatusInternalServerError)
}
if out == nil {
out = make(rc.Params)
}
fs.Debugf(nil, "rc: %q: reply %+v: %v", method, out, err)
err = rc.WriteJSON(buf, out)
var w strings.Builder
err = rc.WriteJSON(&w, out)
if err != nil {
writeError(method, in, buf, err, http.StatusInternalServerError)
return buf.String(), http.StatusInternalServerError
fs.Errorf(nil, "rc: failed to write JSON output: %v", err)
return writeError(method, in, err, http.StatusInternalServerError)
}
return buf.String(), http.StatusOK
return w.String(), http.StatusOK
}
// do nothing here
// do nothing here - necessary for building into a C library
func main() {}