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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/alpha/lib/strncat.S
Initial import
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+/*
+ * arch/alpha/lib/strncat.S
+ * Contributed by Richard Henderson (rth@tamu.edu)
+ *
+ * Append no more than COUNT characters from the null-terminated string SRC
+ * to the null-terminated string DST. Always null-terminate the new DST.
+ *
+ * This differs slightly from the semantics in libc in that we never write
+ * past count, whereas libc may write to count+1. This follows the generic
+ * implementation in lib/string.c and is, IMHO, more sensible.
+ */
+
+ .text
+
+ .align 3
+ .globl strncat
+ .ent strncat
+strncat:
+ .frame $30, 0, $26
+ .prologue 0
+
+ mov $16, $0 # set up return value
+ beq $18, $zerocount
+
+ /* Find the end of the string. */
+
+ ldq_u $1, 0($16) # load first quadword ($16 may be misaligned)
+ lda $2, -1($31)
+ insqh $2, $16, $2
+ andnot $16, 7, $16
+ or $2, $1, $1
+ cmpbge $31, $1, $2 # bits set iff byte == 0
+ bne $2, $found
+
+$loop: ldq $1, 8($16)
+ addq $16, 8, $16
+ cmpbge $31, $1, $2
+ beq $2, $loop
+
+$found: negq $2, $3 # clear all but least set bit
+ and $2, $3, $2
+
+ and $2, 0xf0, $3 # binary search for that set bit
+ and $2, 0xcc, $4
+ and $2, 0xaa, $5
+ cmovne $3, 4, $3
+ cmovne $4, 2, $4
+ cmovne $5, 1, $5
+ addq $3, $4, $3
+ addq $16, $5, $16
+ addq $16, $3, $16
+
+ /* Now do the append. */
+
+ bsr $23, __stxncpy
+
+ /* Worry about the null termination. */
+
+ zapnot $1, $27, $2 # was last byte a null?
+ bne $2, 0f
+ ret
+
+0: cmplt $27, $24, $2 # did we fill the buffer completely?
+ or $2, $18, $2
+ bne $2, 2f
+
+ and $24, 0x80, $2 # no zero next byte
+ bne $2, 1f
+
+ /* Here there are bytes left in the current word. Clear one. */
+ addq $24, $24, $24 # end-of-count bit <<= 1
+2: zap $1, $24, $1
+ stq_u $1, 0($16)
+ ret
+
+1: /* Here we must read the next DST word and clear the first byte. */
+ ldq_u $1, 8($16)
+ zap $1, 1, $1
+ stq_u $1, 8($16)
+
+$zerocount:
+ ret
+
+ .end strncat