drgn/libdrgn/serialize.c
Omar Sandoval 87b7292aa5 Relicense drgn from GPLv3+ to LGPLv2.1+
drgn is currently licensed as GPLv3+. Part of the long term vision for
drgn is that other projects can use it as a library providing
programmatic interfaces for debugger functionality. A more permissive
license is better suited to this goal. We decided on LGPLv2.1+ as a good
balance between software freedom and permissiveness.

All contributors not employed by Meta were contacted via email and
consented to the license change. The only exception was the author of
commit c4fbf7e589 ("libdrgn: fix for compilation error"), who did not
respond. That commit reverted a single line of code to one originally
written by me in commit 640b1c011d ("libdrgn: embed DWARF index in
DWARF info cache").

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2022-11-01 17:05:16 -07:00

175 lines
4.7 KiB
C

// Copyright (c) Meta Platforms, Inc. and affiliates.
// SPDX-License-Identifier: LGPL-2.1-or-later
#include <assert.h>
#include <endian.h>
#include "serialize.h"
static inline uint8_t copy_bits_step(const uint8_t *s, unsigned int src_bit_offset,
unsigned int bit_size,
unsigned int dst_bit_offset, bool lsb0)
{
uint8_t result;
if (lsb0) {
result = s[0] >> src_bit_offset;
if (bit_size > 8 - src_bit_offset)
result |= s[1] << (8 - src_bit_offset);
result <<= dst_bit_offset;
} else {
result = s[0] << src_bit_offset;
if (bit_size > 8 - src_bit_offset)
result |= s[1] >> (8 - src_bit_offset);
result >>= dst_bit_offset;
}
return result;
}
void copy_bits(void *dst, unsigned int dst_bit_offset, const void *src,
unsigned int src_bit_offset, uint64_t bit_size, bool lsb0)
{
assert(dst_bit_offset < 8);
assert(src_bit_offset < 8);
if (bit_size == 0)
return;
uint8_t *d = dst;
const uint8_t *s = src;
uint64_t dst_last_bit = dst_bit_offset + bit_size - 1;
uint8_t dst_first_mask = copy_bits_first_mask(dst_bit_offset, lsb0);
uint8_t dst_last_mask = copy_bits_last_mask(dst_last_bit, lsb0);
if (dst_bit_offset == src_bit_offset) {
/*
* In the common case that the source and destination have the
* same offset, we can use memcpy(), preserving bits at the
* start and/or end if necessary.
*/
uint8_t first_byte = d[0];
uint8_t last_byte = d[dst_last_bit / 8];
memcpy(d, s, dst_last_bit / 8 + 1);
if (dst_bit_offset != 0) {
d[0] = ((first_byte & ~dst_first_mask)
| (d[0] & dst_first_mask));
}
if (dst_last_bit % 8 != 7) {
d[dst_last_bit / 8] = ((last_byte & ~dst_last_mask)
| (d[dst_last_bit / 8] & dst_last_mask));
}
} else if (bit_size <= 8 - dst_bit_offset) {
/* Destination is only one byte. */
uint8_t dst_mask = dst_first_mask & dst_last_mask;
d[0] = ((d[0] & ~dst_mask)
| (copy_bits_step(&s[0], src_bit_offset, bit_size,
dst_bit_offset, lsb0) & dst_mask));
} else {
/* Destination is two or more bytes. */
d[0] = ((d[0] & ~dst_first_mask)
| (copy_bits_step(&s[0], src_bit_offset,
8 - dst_bit_offset, dst_bit_offset,
lsb0) & dst_first_mask));
src_bit_offset += 8 - dst_bit_offset;
size_t si = src_bit_offset / 8;
src_bit_offset %= 8;
size_t di = 1;
while (di < dst_last_bit / 8) {
d[di] = copy_bits_step(&s[si], src_bit_offset, 8, 0,
lsb0);
di++;
si++;
}
d[di] = ((d[di] & ~dst_last_mask)
| (copy_bits_step(&s[si], src_bit_offset,
dst_last_bit % 8 + 1, 0, lsb0)
& dst_last_mask));
}
}
void serialize_bits(void *buf, uint64_t bit_offset, uint64_t uvalue,
uint8_t bit_size, bool little_endian)
{
uint8_t *p;
size_t bits, size;
unsigned char tmp[9];
uint8_t first_mask, last_mask;
assert(bit_size > 0);
assert(bit_size <= 64);
p = (uint8_t *)buf + bit_offset / 8;
bit_offset %= 8;
bits = bit_offset + bit_size;
size = (bits + 7) / 8;
if (little_endian) {
if (size > sizeof(uvalue))
tmp[8] = uvalue >> (64 - bit_offset);
uvalue = htole64(uvalue << bit_offset);
memcpy(tmp, &uvalue, sizeof(uvalue));
/* bit_offset least significant bits. */
first_mask = (1 << bit_offset) - 1;
/* 8 - (bit_offset + bit_size) % 8 most significant bits. */
last_mask = 0xff00 >> -bits % 8;
} else {
unsigned int shift;
shift = -bits % 8;
if (size > sizeof(uvalue)) {
tmp[0] = uvalue >> (64 - shift);
uvalue = htobe64(uvalue << shift);
memcpy(&tmp[1], &uvalue, sizeof(uvalue));
} else {
uvalue = htobe64(uvalue << (64 - bits));
memcpy(&tmp[0], &uvalue, sizeof(uvalue));
}
/* bit_offset most significant bits. */
first_mask = 0xff00 >> bit_offset;
/* 8 - (bit_offset + bit_size) % 8 least significant bits. */
last_mask = (1 << shift) - 1;
}
if (size == 1) {
p[0] = (p[0] & (first_mask | last_mask)) | tmp[0];
} else {
p[0] = (p[0] & first_mask) | tmp[0];
memcpy(p + 1, tmp + 1, size - 2);
p[size - 1] = (p[size - 1] & last_mask) | tmp[size - 1];
}
}
uint64_t deserialize_bits(const void *buf, uint64_t bit_offset,
uint8_t bit_size, bool little_endian)
{
const uint8_t *p;
size_t bits, size;
uint64_t ret = 0;
assert(bit_size > 0);
assert(bit_size <= 64);
p = (const uint8_t *)buf + bit_offset / 8;
bit_offset %= 8;
bits = bit_offset + bit_size;
size = (bits + 7) / 8;
if (little_endian) {
memcpy(&ret, p, min(size, sizeof(ret)));
ret = le64toh(ret) >> bit_offset;
if (size > sizeof(ret))
ret |= (uint64_t)p[8] << (64 - bit_offset);
} else {
unsigned int shift;
if (size > sizeof(ret))
memcpy(&ret, &p[1], sizeof(ret));
else
memcpy((char *)(&ret + 1) - size, p, size);
shift = -bits % 8;
ret = be64toh(ret) >> shift;
if (size > sizeof(ret))
ret |= (uint64_t)p[0] << (64 - shift);
}
return truncate_unsigned(ret, bit_size);
}