fix coding-style as per clang-format

doc/modbus_mapping_new_extend.txt

@@ -0,0 +1,63 @@
+modbus_mapping_new_extend(3)
+=====================
+
+
+NAME
+----
+modbus_mapping_new_extend - allocate four arrays of bits and registers and file registers
+
+
+SYNOPSIS
+--------
+*modbus_mapping_t* modbus_mapping_new_extend(int 'nb_bits', int 'nb_input_bits', int 'nb_registers', int 'nb_input_registers', uint16_t nb_file_register[MODBUS_MAX_REFERENCE_FILES]);*
+
+
+DESCRIPTION
+-----------
+The *modbus_mapping_new_extend()*  calls linkmb:modbus_mapping_new[3] and additionally allocates up to 
+MODBUS_MAX_REFERENCE_FILES (current specification limit it to 10) arrays for file registers.
+
+Each _value_ in the array, which is not 0 allocates _value_ registers in the file of _index_ -1 .
+( The file registers start with "1" for the first file ) 
+
+RETURN VALUE
+------------
+The function shall return the new allocated structure if successful. Otherwise
+it shall return NULL and set errno.
+
+
+ERRORS
+------
+*ENOMEM*::
+Not enough memory
+
+
+EXAMPLE
+-------
+[source,c]
+-------------------
+/* The first value of each array is accessible from the 0 address. */
+mb_mapping = modbus_mapping_new_extend(BITS_ADDRESS + BITS_NB,
+                                INPUT_BITS_ADDRESS + INPUT_BITS_NB,
+                                REGISTERS_ADDRESS + REGISTERS_NB,
+                                INPUT_REGISTERS_ADDRESS + INPUT_REGISTERS_NB,
+                                FILE_REGISTERS_NB[MODBUS_MAX_REFERENCE_FILES]);
+if (mb_mapping == NULL) {
+    fprintf(stderr, "Failed to allocate the mapping: %s\n",
+            modbus_strerror(errno));
+    modbus_free(ctx);
+    return -1;
+}
+-------------------
+
+SEE ALSO
+--------
+linkmb:modbus_mapping_new[3]
+linkmb:modbus_mapping_free[3]
+linkmb:modbus_mapping_new_start_address[3]
+
+
+AUTHORS
+-------
+The libmodbus documentation was written by Stéphane Raimbault
+<stephane.raimbault@gmail.com>

doc/modbus_mapping_new_start_address_extend.txt

@@ -0,0 +1,81 @@
+modbus_mapping_new_start_address_extend(3)
+===================================
+
+
+NAME
+----
+modbus_mapping_new_start_address_extend - allocate four arrays of bits and registers accessible from their starting addresses and file registers
+
+
+SYNOPSIS
+--------
+*modbus_mapping_t* modbus_mapping_new_start_address(int 'start_bits', int 'nb_bits',
+                                                    int 'start_input_bits', int 'nb_input_bits',
+                                                    int 'start_registers', int 'nb_registers',
+                                                    int 'start_input_registers', int 'nb_input_registers',
+                                                    'uint16_t nb_file_register[MODBUS_MAX_REFERENCE_FILES]');*
+
+
+DESCRIPTION
+-----------
+The *modbus_mapping_new_extend()*  calls linkmb:modbus_mapping_new_start_address[3] and additionally allocates up to 
+MODBUS_MAX_REFERENCE_FILES (current specification limit it to 10) arrays for file registers.
+
+Each _value_ in the array, which is not 0 allocates _value_ registers in the file of _index_ -1 .
+( The file registers start with "1" for the first file ) 
+
+[source,c]
+-------------------
+mb_mapping = modbus_mapping_new_start_address_extend(0, 0, 0, 0, 10000, 10, 0, 0,{0,100,0,20,0,0,10000,0,0,0,0});
+-------------------
+
+With this code, 3 file registers ( 2, 4 and 7 ) with the size of 100 , 20  and 10000 registers are allocated.
+
+If it isn't necessary to allocate an array for a specific type of data, you can
+pass the zero value in argument, the associated pointer will be NULL.
+
+This function is convenient to handle requests in a Modbus server/slave.
+
+
+RETURN VALUE
+------------
+The _modbus_mapping_new_start_address_extend()_ function shall return the new allocated structure if
+successful. Otherwise it shall return NULL and set errno.
+
+
+ERRORS
+------
+ENOMEM::
+Not enough memory
+
+
+EXAMPLE
+-------
+[source,c]
+-------------------
+/* The first value of each array is accessible at the defined address.
+   The end address is ADDRESS + NB - 1. */
+mb_mapping = modbus_mapping_new_start_address_extend(BITS_ADDRESS, BITS_NB,
+                                INPUT_BITS_ADDRESS, INPUT_BITS_NB,
+                                REGISTERS_ADDRESS, REGISTERS_NB,
+                                INPUT_REGISTERS_ADDRESS, INPUT_REGISTERS_NB,
+                                FILE_REGISTERS_NB[MODBUS_MAX_REFERENCE_FILES]);
+if (mb_mapping == NULL) {
+    fprintf(stderr, "Failed to allocate the mapping: %s\n",
+            modbus_strerror(errno));
+    modbus_free(ctx);
+    return -1;
+}
+-------------------
+
+SEE ALSO
+--------
+linkmb:modbus_mapping_new_start_address[3]
+linkmb:modbus_mapping_new[3]
+linkmb:modbus_mapping_free[3]
+
+
+AUTHORS
+-------
+The libmodbus documentation was written by Stéphane Raimbault
+<stephane.raimbault@gmail.com>

doc/modbus_read_general_reference.txt

@@ -0,0 +1,84 @@
+modbus_read_general_reference(3)
+========================
+
+
+NAME
+----
+modbus_read_general_reference - read from file registers
+
+
+SYNOPSIS
+--------
+*int modbus_read_general_reference(modbus_t *ctx, int file_no,  int read_addr, int read_nb, uint16_t *dest);*
+
+
+DESCRIPTION
+-----------
+The *modbus_read_general_reference()* function shall read the number of _read_nb_ registers of the _file_no_
+reference file at the address _read_addr_ of the remote device. The result of
+reading is stored in _dest_ array as word values (16 bits).
+
+_file_no_ has to be >= 1 and <= 10 .
+
+You must take care to allocate enough memory to store the results in _dest_
+(at least (_read_nb_ + 1 ) * sizeof(uint16_t)).
+
+The function uses the Modbus function code 0x14 (read file record).
+
+
+RETURN VALUE
+------------
+The function shall return the number of read registers + 1 
+if successful. Otherwise it shall return -1 and set errno.
+
+
+ERRORS
+------
+*EMBMDATA*::
+Too many registers requested
+*EMBXILVAL*::
+_file_no_ out of range , or file is not found.
+
+
+EXAMPLE
+-------
+[source,c]
+-------------------
+modbus_t *ctx;
+uint16_t tab_reg[64+1]; // one additional reg for filesize and reftype
+int rc;
+int i;
+
+ctx = modbus_new_tcp("127.0.0.1", 1502);
+if (modbus_connect(ctx) == -1) {
+    fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
+    modbus_free(ctx);
+    return -1;
+}
+
+ rc = modbus_read_general_reference(ctx, 1, 10 , 64, tab_reg );
+ if (rc == -1) {
+    fprintf(stderr, "%s\n", modbus_strerror(errno));
+    return -1;
+}
+
+printf("size=%d subtype_ref=%d\n", i, tab_reg[0]>>8, tab_reg[0] &0xff);
+for (i=1; i < rc; i++) {
+    printf("reg[%d]=%d (0x%X)\n", i, tab_reg[i], tab_reg[i]);
+}
+
+modbus_close(ctx);
+modbus_free(ctx);
+-------------------
+
+
+SEE ALSO
+--------
+linkmb:modbus_write_general_reference[3]
+linkmb:modbus_mapping_new_start_address_extend[3]
+linkmb:modbus_mapping_new_extend[3]
+
+AUTHORS
+-------
+The libmodbus documentation was written by Stéphane Raimbault
+<stephane.raimbault@gmail.com>

doc/modbus_write_general_reference.txt

@@ -0,0 +1,80 @@
+modbus_write_general_reference(3)
+========================
+
+
+NAME
+----
+modbus_write_general_reference - write to file registers
+
+
+SYNOPSIS
+--------
+*int modbus_write_general_reference(modbus_t *ctx, int file_no,  int write_addr, int write_nb, const uint16_t *src);*
+
+
+DESCRIPTION
+-----------
+The *modbus_read_general_reference()* function shall write the number of _write_nb_ registers of the _file_no_
+reference file at the address _write_addr_ of the remote device. The content for
+writing is delivered in _src_ array as word values (16 bits).
+
+_file_no_ has to be >= 1 and <= 10 .
+
+
+The function uses the Modbus function code 0x15 (write file record).
+
+
+RETURN VALUE
+------------
+The function shall return the number of written registers + 1 
+if successful. Otherwise it shall return -1 and set errno.
+
+
+ERRORS
+------
+*EMBMDATA*::
+Too many registers requested
+*EMBXILVAL*::
+_file_no_ out of range , or file is not found.
+
+
+EXAMPLE
+-------
+[source,c]
+-------------------
+modbus_t *ctx;
+uint16_t tab_reg[64]; 
+int rc;
+int i;
+
+ctx = modbus_new_tcp("127.0.0.1", 1502);
+if (modbus_connect(ctx) == -1) {
+    fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
+    modbus_free(ctx);
+    return -1;
+}
+
+for (i=0; i < 64; i++){
+    tab_reg[i]=i+i*0x100;
+}
+ rc = modbus_write_general_reference(ctx, 1, 10 , 64, tab_reg );
+ if (rc == -1) {
+    fprintf(stderr, "%s\n", modbus_strerror(errno));
+    return -1;
+}
+
+modbus_close(ctx);
+modbus_free(ctx);
+-------------------
+
+
+SEE ALSO
+--------
+linkmb:modbus_read_general_reference[3]
+linkmb:modbus_mapping_new_start_address_extend[3]
+linkmb:modbus_mapping_new_extend[3]
+
+AUTHORS
+-------
+The libmodbus documentation was written by Stéphane Raimbault
+<stephane.raimbault@gmail.com>

src/modbus-private.h

@@ -39,6 +39,9 @@ MODBUS_BEGIN_DECLS
 #define _RESPONSE_TIMEOUT    500000
 #define _BYTE_TIMEOUT        500000
 
+#define SUB_REQUEST_LENGHT   0x07
+#define SUB_REQUEST_REF_TYPE 0x06  // Reference-Type for General Reference Read + Write
+
 typedef enum {
     _MODBUS_BACKEND_TYPE_RTU=0,
     _MODBUS_BACKEND_TYPE_TCP