cpct_memset

Fills up a complete byte-array in memory with a given 8-bit value (as std memset)

C Definition

void cpct_memset (void* array, u8 value, u16 size);

Input Parameters (5 Bytes)

Assembly call (Input parameters on registers)

call cpct_memset_asm

Parameter Restrictions

• array could theoretically be any 16-bit memory location.  However, take into account that this function does no check at all, and you could mistakenly overwrite important parts of your program, the screen, the firmware...  Use it with care.
• size must be greater than 1.  It represents the size of the array, or the number of total bytes that will be set to the value.  As this function starts moving 1 first byte and then cloning it, the minimum amount size should be 2.  Beware!  Sizes 0 and 1 can cause this to overwrite the entire memory.
• value could be any 8-bit value, without restrictions.

Details

Sets all the bytes of an array in memory to the same given value.  This is the same operation as std memset, from the standard C library does.  However, this function is much faster than std C memset, so it is recommended for your productions.  The technique this function uses to be so faster is as follows:

This function works for array sizes from 2 to 65535 (it does not work for 0 or 1).  However, it is recommended that you use it for values greater than 2.  Depending on your code, using memset for values in the range [2-8] could underperform simple variable assignments.

Destroyed Register values

AF, BC, DE, HL

Required memory

Time Measures

  Case     | microSecs (us) | CPU Cycles |
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  Any      |   28 + 6*S     | 112 + 24*S |
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Asm saving |     -18        |    -72     |
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S = size (Number of total bytes to set)