cScale

A SCALE encoding library

What is This?

cScale is a library written in C that adheres to the SCALE (Simple Concatenated Aggregate Little-Endian) codec documented here. It allows for the serialization and deserialization of data into valid SCALE.

It has only one external dependency which is a pure header and included. C99 is generally used except for several C11 _Generic helper definitions.

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Compilation

make all

Default compiler is clang. You can override with CC=gcc make all

This will build all targets, currently:

Target	Generated	Purpose
cli	./cli	Basic command line app
test	./test	Testing app
libcScale.a	./libcScale.a	static library

Link to the generated libcScale.a and copy src/scale.h to your include path. Then include it

#include <scale.h>

Usage

cScale currently supports the following SCALE data types:

Data Type	cScale Structure
Fixed Width Integer	scale_fixed_int
Compact/General Integer	scale_compact_int
Boolean	scale_boolean
Option	scale_option (enum)
Vector	scale_vector
String	scale_vector
Data Structures	User-defined struct containing a scale_structure
Enumeration	scale_enumeration
Tuple	None, helper functions only

Examples

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Serializing and Deserializing a Fixed Width Integer:

scale_fixed_int fixed = { 0 };
encode_int_to_fixed_int_scale(&fixed, (uint16_t)42);
uint8_t serialized[64] = { 0 };
size_t serialized_len = 0;
serialize_fixed_int(serialized, &serialized_len, &fixed);

uint16_t output = 0;
decode_scale_fixed_int((void*)&output, &fixed);

for(int i=0; i < serialized_len; i++) printf("%02X", serialized[i]);
printf(" --- %u\n", output);

Output:

2A00 --- 42

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Serializing and Deserializing a Compact Integer:

  scale_compact_int compact = SCALE_COMPACT_INT_INIT;
  encode_compact(&compact, (uint32_t)69);
  uint8_t serialized[64] = { 0 };
  size_t serialized_len = 0;
  char *output = decode_compact_to_hex(&compact);
  serialize_compact_int(serialized, &serialized_len, &compact);
  uint32_t decoded = strtoul(output, NULL, 16);
  printf("SCALE=<");
  for(int i=0; i < serialized_len; i++) printf("%02X", serialized[i]);
  printf("> --- Hex=<%s> --- Decoded=<%u>\n", output, decoded);
  free(output);

Output:

SCALE=<1501> --- Hex=<45> --- Decoded=<69>

For more information, you can have a look over the docs in doc/ and the test files in src/test/ to see examples of each kind.

Current Status/Limitations

This is a working build that has not been subject to any extensive audits.

Current Limitations:

Type	Reason
u128	C does not support native uint128_t. GCC extension exists but literal u128 values too long. Hex Strings currently used.
Enum	Currently only supporting fixed int/compact int/boolean types
Vector	Due to lack of u128, vector length is currently limited to uint64 max values as max elements. Helper Functions rely on same byte-width elements, such as fixed int or characters. Parsing can be done manually for variable width elements, such as Options.