-----------------------------------------------------------------
+-------------------------------------------------------------------------------
libserialport: cross-platform library for accessing serial ports
-----------------------------------------------------------------
+-------------------------------------------------------------------------------
libserialport is a minimal library written in C that is intended to take care
of the OS-specific details when writing software that uses serial ports.
The API is simple, and designed to be a minimal wrapper around the serial port
support in each OS.
-Most functions take a pointer to a struct sp_port, which represents an open
-port. This structure should be allocated by the user and is populated by
-sp_open(). It can be freed safely after sp_close().
+Most functions take a pointer to a struct sp_port, which represents a serial
+port. These structures are always allocated and freed by the library, using the
+functions in the 'Enumeration' section below.
-All functions can return only two possible error values. SP_ERR_ARG indicates
+All functions can return only three possible error values. SP_ERR_ARG indicates
the function was called with invalid arguments. SP_ERR_FAIL indicates that the
-OS reported a failure. Both these error values are negative.
+OS reported a failure. SP_ERR_MEM indicates that a memory allocation failed.
+All of these error values are negative.
When SP_ERR_FAIL is returned, an error code or string description of the error
can be obtained by calling sp_last_error_code() or sp_last_error_message(). The
error code or message is that provided by the OS; libserialport does not define
any error codes or messages of its own.
-Functions calls that succeed return SP_OK, which is equal to zero, or where
+Function calls that succeed return SP_OK, which is equal to zero, or where
otherwise documented a positive value.
The available functions are as follows:
Enumeration
-----------
-char **sp_list_ports();
+int sp_get_port_by_name(const char *portname, struct sp_port **port_ptr);
- Lists the serial ports available on the system. The value returned is an array
- of port names as C strings, terminated by a NULL. It should be freed after use
- by calling sp_free_port_list().
+ Obtains a pointer to a new sp_port structure representing the named port. The
+ user should allocate a variable of type "struct sp_port *" and pass a pointer
+ to this to receive the result.
-void sp_free_port_list(char **list);
+ The result should be freed after use by calling sp_free_port().
+
+ Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation
+ failure, or SP_ERR_ARG if an invalid pointer is passed. If any error
+ is returned, the variable pointed to by port_ptr will be set to NULL.
+ Otherwise, it will be set to point to the newly allocated port.
- Frees the data structure returned by sp_list_ports().
+void sp_free_port(struct sp_port *port);
+
+ Frees a port structure obtained from sp_get_port_by_name().
+
+int sp_list_ports(struct sp_port ***list_ptr);
+
+ Lists the serial ports available on the system. The result obtained is an
+ array of pointers to sp_port structures, terminated by a NULL. The user should
+ allocate a variable of type "struct sp_port **" and pass a pointer to this to
+ receive the result.
+
+ The result should be freed after use by calling sp_free_port_list(). If a port
+ from the list is to be used after freeing the list, it must be copied first
+ using sp_copy_port().
+
+ Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation
+ failure, or SP_ERR_ARG if an invalid pointer is passed. If any error
+ is returned, the variable pointed to by list_ptr will be set to NULL.
+ Otherwise, it will be set to point to the newly allocated array.
+
+int sp_copy_port(const struct sp_port *port, struct sp_port **copy_ptr);
+
+ Makes a new copy of a sp_port structure. The user should allocate a variable
+ of type "struct sp_port *" and pass a pointer to this to receive the result.
+
+ The copy should be freed after use by calling sp_free_port().
+
+ Returns: SP_OK on success, SP_ERR_MEM on allocation failure, or SP_ERR_ARG
+ if an invalid port or pointer is passed. If any error is returned,
+ the variable pointed to by copy_ptr will be set to NULL. Otherwise,
+ it will be set to point to the newly allocated copy.
+
+void sp_free_port_list(struct sp_port **list);
+
+ Frees a port list obtained from sp_list_ports(). This will also free all
+ the sp_port structures referred to from the list; any that are to be retained
+ must be copied first using sp_copy_port().
Opening and closing ports
-------------------------
-int sp_open(struct sp_port *port, char *portname, int flags);
+int sp_open(struct sp_port *port, int flags);
Opens the specified serial port.
Parameters:
- port: Pointer to empty port structure, allocated by caller.
- portname: Name of port to open.
+ port: Pointer to port structure.
flags: Flags to use when opening the serial port. Possible
flags are: SP_MODE_RDWR, SP_MODE_RDONLY, and SP_MODE_NONBLOCK.
- Returns: SP_OK on success, SP_ERR_FAIL on failure, or SP_ERR_ARG
- if an invalid port or name is passed.
+ Returns: SP_OK on success, SP_ERR_FAIL on failure, SP_ERR_MEM on allocation
+ failure, or SP_ERR_ARG if an invalid port is passed.
int sp_close(struct sp_port *port);
int sp_read(struct sp_port *port, const void *buf, size_t count)
- Reads a number of bytes from the specified serial port.
+ Reads bytes from the specified serial port. Note that this function may
+ return after reading less than the specified number of bytes; it is the
+ user's responsibility to iterate as necessary in this case.
Parameters:
port: Pointer to port structure.
buf: Buffer in which to store the bytes read.
- count: Number of bytes to read.
+ count: Maximum number of bytes to read.
Returns: The number of bytes read, SP_ERR_FAIL on failure,
or SP_ERR_ARG for invalid arguments.
int sp_write(struct sp_port *port, const void *buf, size_t count)
- Writes a number of bytes to the specified serial port.
+ Write bytes to the specified serial port. Note that this function may
+ return after writing less than the specified number of bytes; it is the
+ user's responsibility to iterate as necessary in this case.
Parameters:
port: Pointer to port structure.
buf: Buffer containing the bytes to write.
- count: Number of bytes to write.
+ count: Maximum number of bytes to write.
Returns: The number of bytes written, SP_ERR_FAIL on failure,
or SP_ERR_ARG for invalid arguments.
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