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Support customize FL_INDEX_MAX to reduce the memory overhead #19

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Support customize FL_INDEX_MAX to reduce the memory overhead #19

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46 changes: 29 additions & 17 deletions tlsf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,29 @@
#define TLSF_64BIT
#endif

/*
** Returns one plus the index of the most significant 1-bit of n,
** or if n is zero, returns zero.
*/
#ifdef TLSF_64BIT
#define TLSF_FLS(n) ((n) & 0xffffffff00000000ull ? 32 + TLSF_FLS32((size_t)(n) >> 32) : TLSF_FLS32(n))
#else
#define TLSF_FLS(n) TLSF_FLS32(n)
#endif

#define TLSF_FLS32(n) ((n) & 0xffff0000 ? 16 + TLSF_FLS16((n) >> 16) : TLSF_FLS16(n))
#define TLSF_FLS16(n) ((n) & 0xff00 ? 8 + TLSF_FLS8 ((n) >> 8) : TLSF_FLS8 (n))
#define TLSF_FLS8(n) ((n) & 0xf0 ? 4 + TLSF_FLS4 ((n) >> 4) : TLSF_FLS4 (n))
#define TLSF_FLS4(n) ((n) & 0xc ? 2 + TLSF_FLS2 ((n) >> 2) : TLSF_FLS2 (n))
#define TLSF_FLS2(n) ((n) & 0x2 ? 1 + TLSF_FLS1 ((n) >> 1) : TLSF_FLS1 (n))
#define TLSF_FLS1(n) ((n) & 0x1 ? 1 : 0)
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/*
** Returns round up value of log2(n).
** Note: it is used at compile time.
*/
#define TLSF_LOG2_CEIL(n) ((n) & (n - 1) ? TLSF_FLS(n) : TLSF_FLS(n) - 1)

/*
** gcc 3.4 and above have builtin support, specialized for architecture.
** Some compilers masquerade as gcc; patchlevel test filters them out.
Expand Down Expand Up @@ -147,29 +170,16 @@ tlsf_decl int tlsf_fls(unsigned int word)
#else
/* Fall back to generic implementation. */

tlsf_decl int tlsf_fls_generic(unsigned int word)
{
int bit = 32;

if (!word) bit -= 1;
if (!(word & 0xffff0000)) { word <<= 16; bit -= 16; }
if (!(word & 0xff000000)) { word <<= 8; bit -= 8; }
if (!(word & 0xf0000000)) { word <<= 4; bit -= 4; }
if (!(word & 0xc0000000)) { word <<= 2; bit -= 2; }
if (!(word & 0x80000000)) { word <<= 1; bit -= 1; }

return bit;
}

/* Implement ffs in terms of fls. */
tlsf_decl int tlsf_ffs(unsigned int word)
{
return tlsf_fls_generic(word & (~word + 1)) - 1;
const unsigned int reverse = word & (~word + 1);
return TLSF_FLS32(reverse) - 1;
}

tlsf_decl int tlsf_fls(unsigned int word)
{
return tlsf_fls_generic(word) - 1;
return TLSF_FLS32(word) - 1;
}

#endif
Expand Down Expand Up @@ -234,7 +244,9 @@ enum tlsf_private
** blocks below that size into the 0th first-level list.
*/

#if defined (TLSF_64BIT)
#if defined (TLSF_MAX_POOL_SIZE)
FL_INDEX_MAX = TLSF_LOG2_CEIL(TLSF_MAX_POOL_SIZE),
#elif defined (TLSF_64BIT)
/*
** TODO: We can increase this to support larger sizes, at the expense
** of more overhead in the TLSF structure.
Expand Down