Add Fetch().

rrd.go

@@ -386,3 +386,13 @@ func (g *Grapher) SaveGraph(filename string, start, end time.Time) (GraphInfo, e
 	gi, _, err := g.graph(filename, start, end)
 	return gi, err
 }
+
+type FetchResult struct {
+	Filename string
+	Cf       string
+	Start    time.Time
+	End      time.Time
+	Step     uint64
+	DsNames  []string
+	Values   [][]float64
+}

rrd_c.go

@@ -380,3 +380,47 @@ func Info(filename string) (map[string]interface{}, error) {
 	}
 	return parseRRDInfo(i), nil
 }
+
+// Fetch retrieves data from RRD file.
+func Fetch(filename, cf string, start, end time.Time, step uint64) (FetchResult, error) {
+	fn := C.CString(filename)
+	defer freeCString(fn)
+	cCf := C.CString(cf)
+	defer freeCString(cCf)
+	var ret C.int
+	var cStart C.time_t
+	var cEnd C.time_t
+	var cStep C.ulong
+	var cDsCnt C.ulong
+	var cDsNames **C.char
+	var cData *C.double
+	cStart = C.time_t(start.Unix())
+	cEnd = C.time_t(end.Unix())
+	cStep = C.ulong(step)
+	err := makeError(C.rrdFetch(&ret, fn, cCf, &cStart, &cEnd, &cStep, &cDsCnt, &cDsNames, &cData))
+	if err != nil {
+		return FetchResult{filename, cf, start, end, step, nil, nil}, err
+	}
+
+	start = time.Unix(int64(cStart), 0)
+	end = time.Unix(int64(cEnd), 0)
+	step = uint64(cStep)
+	dsCnt := int(cDsCnt)
+
+	rowLen := (int(cEnd) - int(cStart)) / int(cStep) + 1
+	dsNames := make([]string, dsCnt)
+	rows := make([][]float64, dsCnt)
+	for i := 0; i < dsCnt; i++ {
+		dsName := C.arrayGetCString(cDsNames, C.int(i))
+		dsNames[i] = C.GoString(dsName)
+		C.free(unsafe.Pointer(dsName))
+
+		rows[i] = make([]float64, rowLen)
+		for j := 0; j < rowLen; j++ {
+			rows[i][j] = float64(C.arrayGetDouble(cData, C.int(i * rowLen + j)))
+		}
+	}
+	C.free(unsafe.Pointer(cDsNames))
+	C.free(unsafe.Pointer(cData))
+	return FetchResult{filename, cf, start, end, step, dsNames, rows}, nil
+}

rrd_test.go

@@ -85,4 +85,18 @@ func TestAll(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
+	// Fetch
+	now := time.Now()
+	res, err := Fetch(dbfile, "AVERAGE", now.Add(-20*time.Second), now, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, dsName := range res.DsNames {
+		fmt.Printf("datasource: %s\n", dsName)
+		for j, value := range res.Values[i] {
+			t := res.Start.Add(time.Duration(int(res.Step) * j) * time.Second)
+			fmt.Printf("%s %e\n", t, value)
+		}
+	}
 }

rrdfunc.c

@@ -39,3 +39,17 @@ char *rrdInfo(rrd_info_t **ret, char *filename) {
 	*ret = rrd_info_r(filename);
 	return rrdError();
 }
+
+char *rrdFetch(int *ret, char *filename, const char *cf, time_t *start, time_t *end, unsigned long *step, unsigned long *ds_cnt, char ***ds_namv, double **data) {
+	rrd_clear_error();
+	*ret = rrd_fetch_r(filename, cf, start, end, step, ds_cnt, ds_namv, data);
+	return rrdError();
+}
+
+char *arrayGetCString(char **values, int i) {
+	return values[i];
+}
+
+double arrayGetDouble(double *values, int i) {
+	return values[i];
+}

rrdfunc.h

@@ -2,3 +2,6 @@ extern char *rrdCreate(const char *filename, unsigned long step, time_t start, i
 extern char *rrdUpdate(const char *filename, const char *template, int argc, const char **argv);
 extern char *rrdGraph(rrd_info_t **ret, int argc, char **argv);
 extern char *rrdInfo(rrd_info_t **ret, char *filename);
+extern char *rrdFetch(int *ret, char *filename, const char *cf, time_t *start, time_t *end, unsigned long *step, unsigned long *ds_cnt, char ***ds_namv, double **data);
+extern char *arrayGetCString(char **values, int i);
+extern double arrayGetDouble(double *values, int i);