/* * Copyright (c) 2002 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ #define ASSEMBLER #include #undef ASSEMBLER #define __APPLE_API_PRIVATE #include #undef __APPLE_API_PRIVATE /* We use mode-independent "g" opcodes such as "srgi". These expand * into word operations when targeting __ppc__, and into doubleword * operations when targeting __ppc64__. */ #include // ***************** // * S T R L C A T * // ***************** // // size_t strlcat(char *dst, const char *src, size_t count); // // We optimize the move by doing it word parallel. This introduces // a complication: if we blindly did word load/stores until finding // a 0, we might get a spurious page fault by touching bytes past it. // We are allowed to touch the "count" bytes starting at "dst", but // when appending the "src", we must not do a "lwz" that crosses a page // boundary, or store past "count". // // The test for 0s relies on the following inobvious but very efficient // word-parallel test: // x = dataWord + 0xFEFEFEFF // y = ~dataWord & 0x80808080 // if (x & y) == 0 then no zero found // The test maps any non-zero byte to zero, and any zero byte to 0x80, // with one exception: 0x01 bytes preceeding the first zero are also // mapped to 0x80. // // Note that "count" is the total buffer length, including the length // of the "dst" string. This is different than strncat(). // // In 64-bit mode, this algorithm is doubleword parallel. .text .globl EXT(strlcat) .align 5 LEXT(strlcat) // size_t strlcat(char *dst, const char *src, size_t count); srgi. r0,r5,LOG2_GPR_BYTES// get #words or doublewords to scan #if defined(__ppc__) lis r6,hi16(0xFEFEFEFF) // start to generate 32-bit magic constants lis r7,hi16(0x80808080) ori r6,r6,lo16(0xFEFEFEFF) ori r7,r7,lo16(0x80808080) #else ld r6,_COMM_PAGE_MAGIC_FE(0) // get 0xFEFEFEFE FEFEFEFF from commpage ld r7,_COMM_PAGE_MAGIC_80(0) // get 0x80808080 80808080 from commpage #endif mr r9,r3 // use r9 for dest ptr (r3 remembers dst start) beq-- L0bytes // buffer length <4 mtctr r0 // set up loop b L0words // enter word loop // Loop over words looking for 0. // r3 = original start of buffer // r4 = source ptr (unaligned) // r5 = original buffer size // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) // ctr = #words or doublewords remaining in buffer .align 5 // align inner loops for speed L0words: lg r8,0(r9) // r8 <- next dest word or doubleword addi r9,r9,GPR_BYTES add r10,r8,r6 // r10 <- word + 0xFEFEFEFF andc r12,r7,r8 // r12 <- ~word & 0x80808080 and. r11,r10,r12 // r11 <- nonzero iff word has a 0-byte bdnzt eq,L0words // loop until 0 found or buffer end beq-- L0bytes // skip if 0 not found slgi r0,r8,7 // move 0x01 bits (false hits) into 0x80 position subi r9,r9,GPR_BYTES // back up r9 to the start of the word andc r11,r11,r0 // mask out false hits cntlzg r0,r11 // find 0 byte (r0 = 0, 8, 16, or 24) srwi r0,r0,3 // now r0 = 0, 1, 2, or 3 add r9,r9,r0 // now r9 points to the 0-byte in dest b L0found // start to append source // Loop over bytes looking for 0. // r3 = original start of buffer // r4 = source ptr (unaligned) // r5 = original buffer size // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) L0bytes: andi. r0,r5,GPR_BYTES-1 // get #bytes remaining in buffer mtctr r0 // set up byte loop beq-- L0notfound // skip if 0 not found in buffer (error) L0byteloop: lbz r8,0(r9) // r8 <- next dest byte addi r9,r9,1 cmpwi r8,0 // 0 ? bdnzf eq,L0byteloop // loop until 0 found or buffer end bne-- L0notfound // skip if 0 not found (error) subi r9,r9,1 // back up, so r9 points to the 0 // End of dest found, so we can start appending source. First, align the source, // in order to avoid spurious page faults. // r3 = original start of buffer // r4 = original source ptr (unaligned) // r5 = original buffer size // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = ptr to 0-byte in dest (unaligned) L0found: andi. r0,r4,GPR_BYTES-1 // is source aligned? add r5,r5,r3 // get ptr to end of buffer sub r5,r5,r9 // get #bytes remaining in buffer, counting the 0 (r5>0) beq Laligned // skip if source already word aligned subfic r0,r0,GPR_BYTES // not aligned, get #bytes to align r4 b Lbyteloop1 // r5!=0, so skip check // Copy min(r0,r5) bytes, until 0-byte. // r0 = #bytes we propose to copy (NOTE: must be >0) // r4 = source ptr (unaligned) // r5 = length remaining in buffer (may be 0) // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) Lbyteloop: cmpgi r5,0 // buffer empty? (note: length is unsigned) beq-- Loverrun // buffer filled before end of source reached Lbyteloop1: // entry when we know r5!=0 lbz r8,0(r4) // r8 <- next source byte subic. r0,r0,1 // decrement count of bytes to move addi r4,r4,1 subi r5,r5,1 // decrement buffer length remaining stb r8,0(r9) // pack into dest cmpwi cr1,r8,0 // 0-byte? addi r9,r9,1 beq cr1,L0stored // byte was 0, so done bne Lbyteloop // r0!=0, source not yet aligned // Source is aligned. Loop over words or doublewords until 0-byte found or end // of buffer. // r3 = original start of buffer // r4 = source ptr (aligned) // r5 = length remaining in buffer // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) Laligned: srgi. r8,r5,LOG2_GPR_BYTES// get #words or doublewords in buffer addi r0,r5,1 // if no words... beq-- Lbyteloop // ...copy to end of buffer mtctr r8 // set up loop count rlwinm r5,r5,0,GPR_BYTES-1 // mask buffer length down to leftover bytes b LwordloopEnter // Inner loop: move a word or doubleword at a time, until one of two conditions: // - a zero byte is found // - end of buffer // At this point, registers are as follows: // r3 = original start of buffer // r4 = source ptr (aligned) // r5 = bytes leftover in buffer (0..GPR_BYTES-1) // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r9 = dest ptr (unaligned) // ctr = loop count .align 5 // align inner loop, which is 8 words long Lwordloop: stg r8,0(r9) // pack word into destination addi r9,r9,GPR_BYTES LwordloopEnter: lg r8,0(r4) // r8 <- next 4 or 8 source bytes addi r4,r4,GPR_BYTES add r10,r8,r6 // r10 <- word + 0xFEFEFEFF andc r12,r7,r8 // r12 <- ~word & 0x80808080 and. r11,r10,r12 // r11 <- nonzero iff word has a 0-byte bdnzt eq,Lwordloop // loop if ctr!=0 and cr0_eq beq-- Lleftovers // skip if no 0-byte found, copy leftovers // Found a 0-byte. Store last word up to and including the 0, a byte at a time. // r3 = original start of buffer // r8 = last word, known to have a 0-byte // r9 = dest ptr (one past 0) Lstorelastbytes: srgi. r0,r8,GPR_BYTES*8-8 // right justify next byte and test for 0 slgi r8,r8,8 // shift next byte into position stb r0,0(r9) // pack into dest addi r9,r9,1 bne Lstorelastbytes // loop until 0 stored // Append op successful, O stored into buffer. Return total length. // r3 = original start of buffer // r9 = dest ptr (one past 0) L0stored: sub r3,r9,r3 // get (length+1) of string in buffer subi r3,r3,1 // return length blr // 0-byte not found in aligned source words. There are up to GPR_BYTES-1 leftover // source bytes, hopefully the 0-byte is among them. // r4 = source ptr (aligned) // r5 = leftover bytes in buffer (0..GPR_BYTES-1) // r6 = 0xFEFEFEFF // r7 = 0x80808080 // r8 = last full word or doubleword of source // r9 = dest ptr (unaligned) Lleftovers: stg r8,0(r9) // store last word addi r9,r9,GPR_BYTES addi r0,r5,1 // make sure r5 terminates byte loop (not r0) b Lbyteloop // Buffer filled during append without finding the end of source. Overwrite the // last byte in buffer with a 0, and compute how long the concatenated string would // have been, if the buffer had been large enough. // r3 = original start of buffer // r4 = source ptr (1st byte not copied into buffer) // r9 = dest ptr (one past end of buffer) Loverrun: sub. r3,r9,r3 // compute #bytes stored in buffer li r0,0 // get a 0 beq-- Lskip // buffer was 0-length stb r0,-1(r9) // jam in delimiting 0 // Buffer full, check to see how much longer source is. We don't optimize this, // since overruns are an error. Lskip: lbz r8,0(r4) // get next source byte addi r4,r4,1 addi r3,r3,1 // increment length of "ideal" string cmpwi r8,0 // 0? bne Lskip subi r3,r3,1 // don't count 0 in length blr // return length of string we "wanted" to create // 0 not found in buffer (append not yet begun.) We don't store a delimiting 0, // but do compute how long the concatenated string would have been, assuming the length // of "dst" is the length of the buffer. // r3 = original start of buffer // r4 = original source ptr // r9 = dest ptr (one past end of buffer) L0notfound: sub r3,r9,r3 // compute #bytes in buffer b Lskip // add strlen(source) to r3