fs/jffs2/compr_rubin.c

File Facts

System

Linux kernel

Corpus path

fs/jffs2/compr_rubin.c

Extension

.c

Size

8835 bytes

Lines

448

Domain

Core OS

Bucket

VFS And Filesystem Core

Inferred role

Core OS: implementation source

Status

source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

• Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/string.h
• linux/types.h
• linux/jffs2.h
• linux/errno.h
• compr.h

Detected Declarations

• struct pushpull
• struct rubin_state
• function init_pushpull
• function pushbit
• function pushedbits
• function pullbit
• function init_rubin
• function encode
• function end_rubin
• function init_decode
• function __do_decode
• function decode
• function out_byte
• function in_byte
• function rubin_do_compress
• function jffs2_rubinmips_compress
• function jffs2_dynrubin_compress
• function rubin_do_decompress
• function jffs2_rubinmips_decompress
• function jffs2_dynrubin_decompress
• function jffs2_rubinmips_init
• function jffs2_rubinmips_exit
• function jffs2_dynrubin_init
• function jffs2_dynrubin_exit

Annotated Snippet

struct pushpull {
	unsigned char *buf;
	unsigned int buflen;
	unsigned int ofs;
	unsigned int reserve;
};

struct rubin_state {
	unsigned long p;
	unsigned long q;
	unsigned long rec_q;
	long bit_number;
	struct pushpull pp;
	int bit_divider;
	int bits[8];
};

static inline void init_pushpull(struct pushpull *pp, char *buf,
				 unsigned buflen, unsigned ofs,
				 unsigned reserve)
{
	pp->buf = buf;
	pp->buflen = buflen;
	pp->ofs = ofs;
	pp->reserve = reserve;
}

static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
{
	if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve))
		return -ENOSPC;

	if (bit)
		pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7)));
	else
		pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7)));

	pp->ofs++;

	return 0;
}

static inline int pushedbits(struct pushpull *pp)
{
	return pp->ofs;
}

static inline int pullbit(struct pushpull *pp)
{
	int bit;

	bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;

	pp->ofs++;
	return bit;
}


static void init_rubin(struct rubin_state *rs, int div, int *bits)
{
	int c;

	rs->q = 0;
	rs->p = (long) (2 * UPPER_BIT_RUBIN);
	rs->bit_number = (long) 0;
	rs->bit_divider = div;

	for (c=0; c<8; c++)
		rs->bits[c] = bits[c];
}


static int encode(struct rubin_state *rs, long A, long B, int symbol)
{

	long i0, i1;
	int ret;

	while ((rs->q >= UPPER_BIT_RUBIN) ||
	       ((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
		rs->bit_number++;

		ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
		if (ret)
			return ret;
		rs->q &= LOWER_BITS_RUBIN;
		rs->q <<= 1;
		rs->p <<= 1;
	}
	i0 = A * rs->p / (A + B);

Annotation

• Immediate include surface: `linux/string.h`, `linux/types.h`, `linux/jffs2.h`, `linux/errno.h`, `compr.h`.
• Detected declarations: `struct pushpull`, `struct rubin_state`, `function init_pushpull`, `function pushbit`, `function pushedbits`, `function pullbit`, `function init_rubin`, `function encode`, `function end_rubin`, `function init_decode`.
• Atlas domain: Core OS / VFS And Filesystem Core.
• Implementation status: source implementation candidate.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.