Line data    Source code

       1             : /*-----------------------------------------------------------------------
       2             :  * ascii.h
       3             :  *
       4             :  *   Portions Copyright (c) 1999-2024, PostgreSQL Global Development Group
       5             :  *
       6             :  * src/include/utils/ascii.h
       7             :  *
       8             :  *-----------------------------------------------------------------------
       9             :  */
      10             : 
      11             : #ifndef _ASCII_H_
      12             : #define _ASCII_H_
      13             : 
      14             : #include "port/simd.h"
      15             : 
      16             : extern void ascii_safe_strlcpy(char *dest, const char *src, size_t destsiz);
      17             : 
      18             : /*
      19             :  * Verify a chunk of bytes for valid ASCII.
      20             :  *
      21             :  * Returns false if the input contains any zero bytes or bytes with the
      22             :  * high-bit set. Input len must be a multiple of the chunk size (8 or 16).
      23             :  */
      24             : static inline bool
      25     2886874 : is_valid_ascii(const unsigned char *s, int len)
      26             : {
      27     2886874 :     const unsigned char *const s_end = s + len;
      28             :     Vector8     chunk;
      29     2886874 :     Vector8     highbit_cum = vector8_broadcast(0);
      30             : #ifdef USE_NO_SIMD
      31             :     Vector8     zero_cum = vector8_broadcast(0x80);
      32             : #endif
      33             : 
      34             :     Assert(len % sizeof(chunk) == 0);
      35             : 
      36     8660622 :     while (s < s_end)
      37             :     {
      38     5773748 :         vector8_load(&chunk, s);
      39             : 
      40             :         /* Capture any zero bytes in this chunk. */
      41             : #ifdef USE_NO_SIMD
      42             : 
      43             :         /*
      44             :          * First, add 0x7f to each byte. This sets the high bit in each byte,
      45             :          * unless it was a zero. If any resulting high bits are zero, the
      46             :          * corresponding high bits in the zero accumulator will be cleared.
      47             :          *
      48             :          * If none of the bytes in the chunk had the high bit set, the max
      49             :          * value each byte can have after the addition is 0x7f + 0x7f = 0xfe,
      50             :          * and we don't need to worry about carrying over to the next byte. If
      51             :          * any input bytes did have the high bit set, it doesn't matter
      52             :          * because we check for those separately.
      53             :          */
      54             :         zero_cum &= (chunk + vector8_broadcast(0x7F));
      55             : #else
      56             : 
      57             :         /*
      58             :          * Set all bits in each lane of the highbit accumulator where input
      59             :          * bytes are zero.
      60             :          */
      61     5773748 :         highbit_cum = vector8_or(highbit_cum,
      62             :                                  vector8_eq(chunk, vector8_broadcast(0)));
      63             : #endif
      64             : 
      65             :         /* Capture all set bits in this chunk. */
      66     5773748 :         highbit_cum = vector8_or(highbit_cum, chunk);
      67             : 
      68     5773748 :         s += sizeof(chunk);
      69             :     }
      70             : 
      71             :     /* Check if any high bits in the high bit accumulator got set. */
      72     2886874 :     if (vector8_is_highbit_set(highbit_cum))
      73         984 :         return false;
      74             : 
      75             : #ifdef USE_NO_SIMD
      76             :     /* Check if any high bits in the zero accumulator got cleared. */
      77             :     if (zero_cum != vector8_broadcast(0x80))
      78             :         return false;
      79             : #endif
      80             : 
      81     2885890 :     return true;
      82             : }
      83             : 
      84             : #endif                          /* _ASCII_H_ */