Date: Fri, 24 Feb 2006 22:19:09 +0000
From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Matt Mackall <mpm@selenic.com>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/7] inflate pt1: clean up input logic
Message-ID: <20060224221909.GD28855@flint.arm.linux.org.uk>
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	Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
References: <0.399206195@selenic.com> <4.399206195@selenic.com>
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On Fri, Feb 24, 2006 at 02:12:16PM -0600, Matt Mackall wrote:
> -static const u16 mask_bits[] = {
> -	0x0000,
> -	0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
> -	0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
> -};
> +static inline u32 readbits(u32 *b, u32 *k, int n)
> +{
> +	for( ; *k < n; *k += 8)
> +		*b |= (u32)get_byte() << *k;
> +	return *b & ((1 << n) - 1);
> +}
>  
> -#define NEXTBYTE()  ({ int v = get_byte(); if (v < 0) goto underrun; (u8)v; })

How does this change handle the case where we run out of input data?
This condition needs to be handled explicitly because the inflate
functions can infinitely loop.

Relying on a bit pattern returned by get_byte() is how this code
pre-fix used to work, and it caused several confused bug reports.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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