Byte cursor pulling opcodes sequentially across .ARM.extab words. More...

#include <arm_extab_stream.hpp>

Public Member Functions
constexpr	extab_byte_stream (address_space_ref space, uintptr_t extab_addr) noexcept
	Constructs a stream rooted at the first extab word.

constexpr bool	failed () const noexcept
	Reports whether the stream failed to parse a supported word-0 header (e.g. an out-of-line personality-routine pointer, which cannot be interpreted as bytecode).

bool	next_byte (uint8_t &out_byte) noexcept
	Pulls the next bytecode instruction byte across word boundaries.

Detailed Description

Byte cursor pulling opcodes sequentially across .ARM.extab words.

Per ARM EHABI ("Personality routine exception-handling table entries"), word 0's most-significant byte packs 1 <personality-index(3 bits)> <reserved(4 bits)>-like fields: bit 31 set marks an inline (rather than out-of-line personality-routine-pointer) table entry, and bits 27:24 select one of the three ABI personality routines, which in turn determines how many opcode bytes word 0 contributes and whether a word count follows:

Personality 0 (Su16, Short): word 0 = [1|idx=0][opcode][opcode] [opcode] – 3 opcode bytes, no extra-word count.
Personality 1/2 (Lu16/Lu32, Long): word 0 = [1|idx][N: extra word count][opcode][opcode] – only 2 opcode bytes from word 0, followed by N additional words each contributing 4 more opcode bytes (MSB first).

Constructor & Destructor Documentation

◆ extab_byte_stream()

constexpr microfmt::extab_byte_stream::extab_byte_stream	(	address_space_ref	space,
		uintptr_t	extab_addr
	)

inlineconstexprnoexcept

Constructs a stream rooted at the first extab word.

Parameters

space	Address space to read from.
extab_addr	Address of the `.ARM.extab` entry.

Member Function Documentation

◆ failed()

constexpr bool microfmt::extab_byte_stream::failed ( ) const

inlineconstexprnoexcept

Reports whether the stream failed to parse a supported word-0 header (e.g. an out-of-line personality-routine pointer, which cannot be interpreted as bytecode).

◆ next_byte()

bool microfmt::extab_byte_stream::next_byte ( uint8_t & out_byte )

inlinenoexcept

Pulls the next bytecode instruction byte across word boundaries.