xref: /isa-l/mem/mem_zero_detect_base.c (revision aaa78d6a7c0a3e3a48e4997bd5b8f78e71070835)

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  modification, are permitted provided that the following conditions
  are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
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      notice, this list of conditions and the following disclaimer in
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      distribution.
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#include <stdint.h>
#include <stddef.h>
#include "unaligned.h"

int
mem_zero_detect_base(void *buf, size_t n)
{
        uint8_t *c = buf;
        uintmax_t a = 0;

        // Check buffer in native machine width comparisons
        while (n >= sizeof(uintmax_t)) {
                n -= sizeof(uintmax_t);
                if (load_le_umax(c) != 0)
                        return -1;
                c += sizeof(uintmax_t);
        }

        // Check remaining bytes
        switch (n) {
        case 7:
                a |= *c++; // fall through to case 6,5,4
        case 6:
                a |= *c++; // fall through to case 5,4
        case 5:
                a |= *c++; // fall through to case 4
        case 4:
                a |= load_le_u32(c);
                break;
        case 3:
                a |= *c++; // fall through to case 2
        case 2:
                a |= load_le_u16(c);
                break;
        case 1:
                a |= *c;
                break;
        }

        return (a == 0) ? 0 : -1;
}