datastore.c: Improve error handling and docs.

- Add Doxygen comments for all functions (some TODOs remain).

 - Check for invalid input parameters (such as NULL pointers etc).

 - Return SR_ERR_ARG upon invalid input parameters.

 - Make sr_datastore_put() return int instead of void, so we can pass
   an error code (SR_OK, SR_ERR_MALLOC, and so on) to the caller.

datastore.c

@@ -26,13 +26,40 @@
 
 static gpointer new_chunk(struct sr_datastore **ds);
 
+/**
+ * Create a new datastore with the specified unit size.
+ *
+ * The unit size is fixed once the datastore is created, and cannot be
+ * changed later on, neither can data be added to the datastore with
+ * different unit sizes later.
+ *
+ * It is the caller's responsibility to free the allocated memory of the
+ * datastore via the sr_datastore_destroy() function, if no longer needed.
+ *
+ * TODO: Unitsize should probably be unsigned int or uint32_t or similar.
+ * TODO: This function should have a 'chunksize' parameter, and
+ *       struct sr_datastore a 'chunksize' field.
+ *
+ * @param unitsize The unit size (>= 1) to be used for this datastore.
+ * @param ds Pointer to a variable which will hold the newly created
+ *           datastore structure.
+ *           
+ * @return SR_OK upon success, SR_ERR_MALLOC upon memory allocation errors,
+ *         or SR_ERR_ARG upon invalid arguments. If something other than SR_OK
+ *         is returned, the value of 'ds' is undefined.
+ */
 int sr_datastore_new(int unitsize, struct sr_datastore **ds)
 {
-	if (!ds)
+	if (!ds) {
-		return SR_ERR;
+		sr_err("ds: %s: ds was NULL", __func__);
+		return SR_ERR_ARG;
+	}
 
-	if (unitsize <= 0)
+	if (unitsize <= 0) {
-		return SR_ERR; /* TODO: Different error? */
+		sr_err("ds: %s: unitsize was %d, but it must be >= 1",
+		       __func__, unitsize);
+		return SR_ERR_ARG;
+	}
 
 	if (!(*ds = g_try_malloc(sizeof(struct sr_datastore)))) {
 		sr_err("ds: %s: ds malloc failed", __func__);
@@ -46,22 +73,63 @@ int sr_datastore_new(int unitsize, struct sr_datastore **ds)
 	return SR_OK;
 }
 
+/**
+ * Destroy the specified datastore and free the memory used by it.
+ *
+ * This will free the memory used by the data in the datastore's 'chunklist',
+ * by the chunklist data structure itself, and by the datastore struct.
+ *
+ * @param ds The datastore to destroy.
+ *
+ * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments.
+ */
 int sr_datastore_destroy(struct sr_datastore *ds)
 {
 	GSList *chunk;
 
-	if (!ds)
+	if (!ds) {
-		return SR_ERR;
+		sr_err("ds: %s: ds was NULL", __func__);
+		return SR_ERR_ARG;
+	}
 
 	for (chunk = ds->chunklist; chunk; chunk = chunk->next)
 		g_free(chunk->data);
 	g_slist_free(ds->chunklist);
 	g_free(ds);
 
+	/* TODO: Set ds = NULL? */
+
 	return SR_OK;
 }
 
-void sr_datastore_put(struct sr_datastore *ds, void *data, unsigned int length,
+/**
+ * Append some data to the specified datastore.
+ *
+ * TODO: More elaborate function description.
+ *
+ * TODO: This function should use the (not yet available) 'chunksize' field
+ *       of struct sr_datastore (instead of hardcoding DATASTORE_CHUNKSIZE).
+ * TODO: in_unitsize and probelist are unused?
+ * TODO: A few of the parameters can be const.
+ * TODO: Handle new_chunk() returning NULL.
+ * TODO: Ideally, 'ds' should be unmodified upon errors.
+ *
+ * @param ds Pointer to the datastore which shall receive the data.
+ *           Must not be NULL.
+ * @param data Pointer to the memory buffer containing the data to add.
+ *             Must not be NULL. TODO: Data format?
+ * @param length Length of the data to add (in number of bytes).
+ *               TODO: Should 0 be allowed as length?
+ * @param in_unitsize The unit size (>= 1) of the input data.
+ * @param probelist Pointer to a list of integers (probe numbers). The probe
+ *                  numbers in this list are 1-based, i.e. the first probe
+ *                  is expected to be numbered 1 (not 0!). Must not be NULL.
+ *
+ * @return SR_OK upon success, SR_ERR_MALLOC upon memory allocation errors,
+ *         or SR_ERR_ARG upon invalid arguments. If something other than SR_OK
+ *         is returned, the value/state of 'ds' is undefined.
+ */
+int sr_datastore_put(struct sr_datastore *ds, void *data, unsigned int length,
 		     int in_unitsize, int *probelist)
 {
 	unsigned int stored;
@@ -72,18 +140,49 @@ void sr_datastore_put(struct sr_datastore *ds, void *data, unsigned int length,
 	(void)in_unitsize;
 	(void)probelist;
 
+	if (!ds) {
+		sr_err("ds: %s: ds was NULL", __func__);
+		return SR_ERR_ARG;
+	}
+
+	/* Unitsize must not be 0, we'll divide by 0 otherwise. */
+	if (ds->ds_unitsize == 0) {
+		sr_err("ds: %s: ds->ds_unitsize was 0", __func__);
+		return SR_ERR_ARG;
+	}
+
+	if (!data) {
+		sr_err("ds: %s: data was NULL", __func__);
+		return SR_ERR_ARG;
+	}
+
+	if (in_unitsize < 1) {
+		sr_err("ds: %s: in_unitsize was %d, but it must be >= 1",
+		       __func__, in_unitsize);
+		return SR_ERR_ARG;
+	}
+
+	if (!probelist) {
+		sr_err("ds: %s: probelist was NULL", __func__);
+		return SR_ERR_ARG;
+	}
+
+	/* Get the last chunk in the list, or create a new one if needed. */
 	if (ds->chunklist == NULL)
 		chunk = new_chunk(&ds);
 	else
 		chunk = g_slist_last(ds->chunklist)->data;
 
+	/* Get/calculate number of chunks, free space, etc. */
 	num_chunks = g_slist_length(ds->chunklist);
 	capacity = (num_chunks * DATASTORE_CHUNKSIZE);
 	chunk_bytes_free = capacity - (ds->ds_unitsize * ds->num_units);
 	chunk_offset = capacity - (DATASTORE_CHUNKSIZE * (num_chunks - 1))
 		       - chunk_bytes_free;
+
 	stored = 0;
 	while (stored < length) {
+		/* No more free space left, allocate a new chunk. */
 		if (chunk_bytes_free == 0) {
 			chunk = new_chunk(&ds);
 			chunk_bytes_free = DATASTORE_CHUNKSIZE;
@@ -100,17 +199,45 @@ void sr_datastore_put(struct sr_datastore *ds, void *data, unsigned int length,
 		chunk_bytes_free -= size;
 		stored += size;
 	}
+
 	ds->num_units += stored / ds->ds_unitsize;
+
+	return SR_OK;
 }
 
+/**
+ * Allocate a new memory chunk, append it to the datastore's chunklist.
+ *
+ * The newly allocated chunk is added to the datastore's chunklist by this
+ * function, and the return value additionally points to the new chunk.
+ *
+ * The allocated memory is guaranteed to be cleared.
+ *
+ * TODO: This function should use the datastore's 'chunksize' field instead
+ *       of hardcoding DATASTORE_CHUNKSIZE.
+ * TODO: Return int, so we can return SR_OK / SR_ERR_ARG / SR_ERR_MALLOC?
+ *
+ * @param ds Pointer to a variable which holds the datastore structure.
+ *           Must not be NULL. The contents of 'ds' are modified in-place.
+ *
+ * @return Pointer to the newly allocated chunk, or NULL upon failure.
+ */
 static gpointer new_chunk(struct sr_datastore **ds)
 {
 	gpointer chunk;
 
-	if (!(chunk = malloc(DATASTORE_CHUNKSIZE * (*ds)->ds_unitsize)))
+	if (!ds) {
-		return NULL;
+		sr_err("ds: %s: ds was NULL", __func__);
+		return NULL; /* TODO: SR_ERR_ARG later? */
+	}
+
+	chunk = g_try_malloc0(DATASTORE_CHUNKSIZE * (*ds)->ds_unitsize);
+	if (!chunk) {
+		sr_err("ds: %s: chunk malloc failed", __func__);
+		return NULL; /* TODO: SR_ERR_MALLOC later? */
+	}
 
 	(*ds)->chunklist = g_slist_append((*ds)->chunklist, chunk);
 
-	return chunk;
+	return chunk; /* TODO: SR_OK later? */
 }

sigrok-proto.h

@@ -34,7 +34,7 @@ int sr_get_loglevel(void);
 
 int sr_datastore_new(int unitsize, struct sr_datastore **ds);
 int sr_datastore_destroy(struct sr_datastore *ds);
-void sr_datastore_put(struct sr_datastore *ds, void *data, unsigned int length,
+int sr_datastore_put(struct sr_datastore *ds, void *data, unsigned int length,
 		     int in_unitsize, int *probelist);
 
 /*--- device.c --------------------------------------------------------------*/