Fg-optional-arabic.bin -

# Write header + body with open(output_bin_path, 'wb') as out: out.write(magic) out.write(struct.pack('<I', version)) out.write(struct.pack('<I', rule_count)) out.write(struct.pack('<I', 16)) # offset to body (after header) out.write(body)

# Hypothetical compiler hb-compile-features -f optional-arabic.txt -o fg-optional-arabic.bin 4.1 Loading in a C/C++ Application #include <stdio.h> #include <stdint.h> typedef struct uint32_t magic; uint32_t version; uint32_t rule_count; uint32_t body_offset; FGHeader; fg-optional-arabic.bin

// ... load rule table from body_offset fclose(f); return hdr; # Write header + body with open(output_bin_path, 'wb')

# Write each rule as: input_len (1B), inputs (4B each), output_len (1B), outputs (4B each), priority (1B) for rule in rules: inputs = rule['input'] outputs = rule['output'] if isinstance(rule['output'], list) else [rule['output']] 'wb') as out: out.write(magic) out.write(struct.pack('&lt

body.append(len(inputs)) for ch in inputs: body.extend(struct.pack('<I', ch)) # Unicode codepoint

def parse_header(self): self.magic = self.data[:4] self.version = int.from_bytes(self.data[4:8], 'little') self.rule_count = int.from_bytes(self.data[8:12], 'little') # ... parse rules When shaping Arabic text, after mandatory shaping, apply optional rules:

body.append(len(outputs)) for out in outputs: body.extend(struct.pack('<I', out))