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Replace PB_MANY_FIELDS with PB_FIELD_16BIT and PB_FIELD_32BIT.

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This allows more precise control over the memory use vs. field size.
This commit is contained in:
Petteri Aimonen
2012-07-01 10:15:37 +03:00
parent 78086cc27d
commit 9b1e1b440a
3 changed files with 65 additions and 34 deletions
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17
docs/reference.rst
View File

@@ -10,14 +10,21 @@ Compilation options
===================
The following options can be specified using -D switch given to the C compiler:
============================ ==============================================================================================
============================ ================================================================================================
__BIG_ENDIAN__ Set this if your platform stores integers and floats in big-endian format.
Mixed-endian systems (different layout for ints and floats) are currently not supported.
NANOPB_INTERNALS Set this to expose the field encoder functions that are hidden since nanopb-0.1.3.
PB_MAX_REQUIRED_FIELDS Maximum number of required fields to check for presence. Default value is 64.
PB_MANY_FIELDS Add support for tag numbers > 255 and fields larger than 255 bytes or 255 array entries.
PB_MAX_REQUIRED_FIELDS Maximum number of required fields to check for presence. Default value is 64. Increases stack
usage 1 byte per every 8 fields. Compiler warning will tell if you need this.
PB_FIELD_16BIT Add support for tag numbers > 255 and fields larger than 255 bytes or 255 array entries.
Increases code size 3 bytes per each field. Compiler error will tell if you need this.
PB_FIELD_32BIT Add support for tag numbers > 65535 and fields larger than 65535 bytes or 65535 array entries.
Increases code size 9 bytes per each field. Compiler error will tell if you need this.
============================ ==============================================================================================
============================ ================================================================================================
The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow raising some datatype limits to suit larger messages.
Their need is recognized automatically by C-preprocessor #if-directives in the generated .pb.h files. The default setting is to use
the smallest datatypes (least resources used).
pb.h
====
@@ -79,7 +86,7 @@ Describes a single structure field with memory position in relation to others. T
:array_size: Maximum number of entries in an array, if it is an array type.
:ptr: Pointer to default value for optional fields, or to submessage description for PB_LTYPE_SUBMESSAGE.
The *uint8_t* datatypes limit the maximum size of a single item to 255 bytes and arrays to 255 items. Compiler will give error if the values are too large. The types can be changed to larger ones by defining *PB_MANY_FIELDS*.
The *uint8_t* datatypes limit the maximum size of a single item to 255 bytes and arrays to 255 items. Compiler will give error if the values are too large. The types can be changed to larger ones by defining *PB_FIELD_16BIT*.
pb_bytes_array_t
----------------

57
generator/nanopb_generator.py
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@@ -252,19 +252,17 @@ class Field:
return result
def needs_32bit_pb_field_t(self):
'''Determine if this field needs 32bit pb_field_t structure to compile properly.
Returns True, False or a C-expression for assert.'''
if self.tag > 255 or self.max_size > 255:
return True
def largest_field_value(self):
'''Determine if this field needs 16bit or 32bit pb_field_t structure to compile properly.
Returns numeric value or a C-expression for assert.'''
if self.ltype == 'PB_LTYPE_SUBMESSAGE':
if self.htype == 'PB_HTYPE_ARRAY':
return 'pb_membersize(%s, %s[0]) > 255' % (self.struct_name, self.name)
return 'pb_membersize(%s, %s[0])' % (self.struct_name, self.name)
else:
return 'pb_membersize(%s, %s) > 255' % (self.struct_name, self.name)
return 'pb_membersize(%s, %s)' % (self.struct_name, self.name)
return max(self.tag, self.max_size, self.max_count)
return False
class Message:
def __init__(self, names, desc):
@@ -426,27 +424,40 @@ def generate_header(dependencies, headername, enums, messages):
yield ' setting PB_MAX_REQUIRED_FIELDS to %d or more.\n' % largest_count
yield '#endif\n'
worst = False
worst = 0
worst_field = ''
checks = []
for msg in messages:
for field in msg.fields:
status = field.needs_32bit_pb_field_t()
if status == True:
worst = True
worst_field = str(field.struct_name) + '.' + str(field.name)
elif status != False:
if worst == False:
status = field.largest_field_value()
if isinstance(status, (str, unicode)):
checks.append(status)
elif status > worst:
worst = status
elif worst != True:
worst += ' || ' + status
worst_field = str(field.struct_name) + '.' + str(field.name)
if worst != False:
if worst > 255 or checks:
yield '\n/* Check that field information fits in pb_field_t */\n'
yield '#ifndef PB_MANY_FIELDS\n'
if worst == True:
yield '#error Field descriptor for %s is too large. Define PB_MANY_FIELDS to fix this.\n' % worst_field
yield '/* (Largest message has %d fields' % worst
if checks: yield ' and submessages have to be checked at compile-time.'
yield ') */\n'
if worst < 65536:
yield '#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)\n'
if worst > 255:
yield '#error Field descriptor for %s is too large. Define PB_FIELD_16BIT to fix this.\n' % worst_field
else:
yield 'STATIC_ASSERT(!(%s), YOU_MUST_DEFINE_PB_MANY_FIELDS)\n' % worst
assertion = ' && '.join(str(c) + ' < 256' for c in checks)
yield 'STATIC_ASSERT((%s), YOU_MUST_DEFINE_PB_FIELD_16BIT)\n' % assertion
yield '#endif\n\n'
if worst > 65535 or checks:
yield '#if !defined(PB_FIELD_32BIT)\n'
if worst > 65535:
yield '#error Field descriptor for %s is too large. Define PB_FIELD_32BIT to fix this.\n' % worst_field
else:
assertion = ' && '.join(str(c) + ' < 65536' for c in checks)
yield 'STATIC_ASSERT((%s), YOU_MUST_DEFINE_PB_FIELD_32BIT)\n' % assertion
yield '#endif\n'
# End of header

19
pb.h
View File

@@ -33,6 +33,11 @@
#define PB_MAX_REQUIRED_FIELDS 64
#endif
#if PB_MAX_REQUIRED_FIELDS < 64
#warning You should not lower PB_MAX_REQUIRED_FIELDS from the default value (64). \
The automatic checks against too low value will not be active.
#endif
/* List of possible field types. These are used in the autogenerated code.
* Least-significant 4 bits tell the scalar type
* Most-significant 4 bits specify repeated/required/packed etc.
@@ -99,21 +104,29 @@ typedef enum {
/* This structure is used in auto-generated constants
* to specify struct fields.
* You can change field sizes here if you need structures
* You can change field sizes if you need structures
* larger than 256 bytes or field tags larger than 256.
* The compiler should complain if your .proto has such
* structures ("initializer too large for type").
* structures. Fix that by defining PB_FIELD_16BIT or
* PB_FIELD_32BIT.
*/
typedef struct _pb_field_t pb_field_t;
struct _pb_field_t {
#ifndef PB_MANY_FIELDS
#if !defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
uint8_t tag;
pb_type_t type;
uint8_t data_offset; /* Offset of field data, relative to previous field. */
int8_t size_offset; /* Offset of array size or has-boolean, relative to data */
uint8_t data_size; /* Data size in bytes for a single item */
uint8_t array_size; /* Maximum number of entries in array */
#elif defined(PB_FIELD_16BIT) && !defined(PB_FIELD_32BIT)
uint16_t tag;
pb_type_t type;
uint8_t data_offset;
int8_t size_offset;
uint16_t data_size;
uint16_t array_size;
#else
uint32_t tag;
pb_type_t type;