diff options
| -rw-r--r-- | cores/arduino/malloc.c | 380 |
1 files changed, 380 insertions, 0 deletions
diff --git a/cores/arduino/malloc.c b/cores/arduino/malloc.c new file mode 100644 index 0000000..9c56600 --- /dev/null +++ b/cores/arduino/malloc.c @@ -0,0 +1,380 @@ +/* Copyright (c) 2002, 2004, 2010 Joerg Wunsch + Copyright (c) 2010 Gerben van den Broeke + All rights reserved. + + malloc, free, realloc from avr-libc 1.7.0 + with minor modifications, by Paul Stoffregen + + Redistribution and use in source and binary forms, with or without + 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. + + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in + the documentation and/or other materials provided with the + distribution. + + * Neither the name of the copyright holders nor the names of + 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 A PARTICULAR PURPOSE + ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + POSSIBILITY OF SUCH DAMAGE. +*/ + + +#include <stdlib.h> +#include <inttypes.h> +#include <string.h> +#include <avr/io.h> + + +#define __MALLOC_MARGIN__ 120 + + +struct __freelist { + size_t sz; + struct __freelist *nx; +}; + +/* + * Exported interface: + * + * When extending the data segment, the allocator will not try to go + * beyond the current stack limit, decreased by __malloc_margin bytes. + * Thus, all possible stack frames of interrupt routines that could + * interrupt the current function, plus all further nested function + * calls must not require more stack space, or they'll risk to collide + * with the data segment. + */ + + +#define STACK_POINTER() ((char *)AVR_STACK_POINTER_REG) +extern char __heap_start; +char *__brkval = &__heap_start; // first location not yet allocated +struct __freelist *__flp; // freelist pointer (head of freelist) +char *__brkval_maximum = 100; + +void * +malloc(size_t len) +{ + struct __freelist *fp1, *fp2, *sfp1, *sfp2; + char *cp; + size_t s, avail; + + /* + * Our minimum chunk size is the size of a pointer (plus the + * size of the "sz" field, but we don't need to account for + * this), otherwise we could not possibly fit a freelist entry + * into the chunk later. + */ + if (len < sizeof(struct __freelist) - sizeof(size_t)) + len = sizeof(struct __freelist) - sizeof(size_t); + + /* + * First, walk the free list and try finding a chunk that + * would match exactly. If we found one, we are done. While + * walking, note down the smallest chunk we found that would + * still fit the request -- we need it for step 2. + * + */ + for (s = 0, fp1 = __flp, fp2 = 0; + fp1; + fp2 = fp1, fp1 = fp1->nx) { + if (fp1->sz < len) + continue; + if (fp1->sz == len) { + /* + * Found it. Disconnect the chunk from the + * freelist, and return it. + */ + if (fp2) + fp2->nx = fp1->nx; + else + __flp = fp1->nx; + return &(fp1->nx); + } + else { + if (s == 0 || fp1->sz < s) { + /* this is the smallest chunk found so far */ + s = fp1->sz; + sfp1 = fp1; + sfp2 = fp2; + } + } + } + /* + * Step 2: If we found a chunk on the freelist that would fit + * (but was too large), look it up again and use it, since it + * is our closest match now. Since the freelist entry needs + * to be split into two entries then, watch out that the + * difference between the requested size and the size of the + * chunk found is large enough for another freelist entry; if + * not, just enlarge the request size to what we have found, + * and use the entire chunk. + */ + if (s) { + if (s - len < sizeof(struct __freelist)) { + /* Disconnect it from freelist and return it. */ + if (sfp2) + sfp2->nx = sfp1->nx; + else + __flp = sfp1->nx; + return &(sfp1->nx); + } + /* + * Split them up. Note that we leave the first part + * as the new (smaller) freelist entry, and return the + * upper portion to the caller. This saves us the + * work to fix up the freelist chain; we just need to + * fixup the size of the current entry, and note down + * the size of the new chunk before returning it to + * the caller. + */ + cp = (char *)sfp1; + s -= len; + cp += s; + sfp2 = (struct __freelist *)cp; + sfp2->sz = len; + sfp1->sz = s - sizeof(size_t); + return &(sfp2->nx); + } + /* + * Step 3: If the request could not be satisfied from a + * freelist entry, just prepare a new chunk. This means we + * need to obtain more memory first. The largest address just + * not allocated so far is remembered in the brkval variable. + * Under Unix, the "break value" was the end of the data + * segment as dynamically requested from the operating system. + * Since we don't have an operating system, just make sure + * that we don't collide with the stack. + */ + cp = STACK_POINTER() - __MALLOC_MARGIN__; + if (cp <= __brkval) + /* + * Memory exhausted. + */ + return 0; + avail = cp - __brkval; + /* + * Both tests below are needed to catch the case len >= 0xfffe. + */ + if (avail >= len && avail >= len + sizeof(size_t)) { + fp1 = (struct __freelist *)__brkval; + __brkval += len + sizeof(size_t); + __brkval_maximum = __brkval; + fp1->sz = len; + return &(fp1->nx); + } + /* + * Step 4: There's no help, just fail. :-/ + */ + return 0; +} + + +void +free(void *p) +{ + struct __freelist *fp1, *fp2, *fpnew; + char *cp1, *cp2, *cpnew; + + /* ISO C says free(NULL) must be a no-op */ + if (p == 0) + return; + + cpnew = p; + cpnew -= sizeof(size_t); + fpnew = (struct __freelist *)cpnew; + fpnew->nx = 0; + + /* + * Trivial case first: if there's no freelist yet, our entry + * will be the only one on it. If this is the last entry, we + * can reduce __brkval instead. + */ + if (__flp == 0) { + if ((char *)p + fpnew->sz == __brkval) + __brkval = cpnew; + else + __flp = fpnew; + return; + } + + /* + * Now, find the position where our new entry belongs onto the + * freelist. Try to aggregate the chunk with adjacent chunks + * if possible. + */ + for (fp1 = __flp, fp2 = 0; + fp1; + fp2 = fp1, fp1 = fp1->nx) { + if (fp1 < fpnew) + continue; + cp1 = (char *)fp1; + fpnew->nx = fp1; + if ((char *)&(fpnew->nx) + fpnew->sz == cp1) { + /* upper chunk adjacent, assimilate it */ + fpnew->sz += fp1->sz + sizeof(size_t); + fpnew->nx = fp1->nx; + } + if (fp2 == 0) { + /* new head of freelist */ + __flp = fpnew; + return; + } + break; + } + /* + * Note that we get here either if we hit the "break" above, + * or if we fell off the end of the loop. The latter means + * we've got a new topmost chunk. Either way, try aggregating + * with the lower chunk if possible. + */ + fp2->nx = fpnew; + cp2 = (char *)&(fp2->nx); + if (cp2 + fp2->sz == cpnew) { + /* lower junk adjacent, merge */ + fp2->sz += fpnew->sz + sizeof(size_t); + fp2->nx = fpnew->nx; + } + /* + * If there's a new topmost chunk, lower __brkval instead. + */ + for (fp1 = __flp, fp2 = 0; + fp1->nx != 0; + fp2 = fp1, fp1 = fp1->nx) + /* advance to entry just before end of list */; + cp2 = (char *)&(fp1->nx); + if (cp2 + fp1->sz == __brkval) { + if (fp2 == NULL) + /* Freelist is empty now. */ + __flp = NULL; + else + fp2->nx = NULL; + __brkval = cp2 - sizeof(size_t); + } +} + + + +void * +realloc(void *ptr, size_t len) +{ + struct __freelist *fp1, *fp2, *fp3, *ofp3; + char *cp, *cp1; + void *memp; + size_t s, incr; + + /* Trivial case, required by C standard. */ + if (ptr == 0) + return malloc(len); + + cp1 = (char *)ptr; + cp1 -= sizeof(size_t); + fp1 = (struct __freelist *)cp1; + + cp = (char *)ptr + len; /* new next pointer */ + if (cp < cp1) + /* Pointer wrapped across top of RAM, fail. */ + return 0; + + /* + * See whether we are growing or shrinking. When shrinking, + * we split off a chunk for the released portion, and call + * free() on it. Therefore, we can only shrink if the new + * size is at least sizeof(struct __freelist) smaller than the + * previous size. + */ + if (len <= fp1->sz) { + /* The first test catches a possible unsigned int + * rollover condition. */ + if (fp1->sz <= sizeof(struct __freelist) || + len > fp1->sz - sizeof(struct __freelist)) + return ptr; + fp2 = (struct __freelist *)cp; + fp2->sz = fp1->sz - len - sizeof(size_t); + fp1->sz = len; + free(&(fp2->nx)); + return ptr; + } + + /* + * If we get here, we are growing. First, see whether there + * is space in the free list on top of our current chunk. + */ + incr = len - fp1->sz; + cp = (char *)ptr + fp1->sz; + fp2 = (struct __freelist *)cp; + for (s = 0, ofp3 = 0, fp3 = __flp; + fp3; + ofp3 = fp3, fp3 = fp3->nx) { + if (fp3 == fp2 && fp3->sz + sizeof(size_t) >= incr) { + /* found something that fits */ + if (fp3->sz + sizeof(size_t) - incr > sizeof(struct __freelist)) { + /* split off a new freelist entry */ + cp = (char *)ptr + len; + fp2 = (struct __freelist *)cp; + fp2->nx = fp3->nx; + fp2->sz = fp3->sz - incr; + fp1->sz = len; + } else { + /* it just fits, so use it entirely */ + fp1->sz += fp3->sz + sizeof(size_t); + fp2 = fp3->nx; + } + if (ofp3) + ofp3->nx = fp2; + else + __flp = fp2; + return ptr; + } + /* + * Find the largest chunk on the freelist while + * walking it. + */ + if (fp3->sz > s) + s = fp3->sz; + } + /* + * If we are the topmost chunk in memory, and there was no + * large enough chunk on the freelist that could be re-used + * (by a call to malloc() below), quickly extend the + * allocation area if possible, without need to copy the old + * data. + */ + if (__brkval == (char *)ptr + fp1->sz && len > s) { + cp = (char *)ptr + len; + cp1 = STACK_POINTER() - __MALLOC_MARGIN__; + if (cp < cp1) { + __brkval = cp; + __brkval_maximum = cp; + fp1->sz = len; + return ptr; + } + /* If that failed, we are out of luck. */ + return 0; + } + + /* + * Call malloc() for a new chunk, then copy over the data, and + * release the old region. + */ + if ((memp = malloc(len)) == 0) + return 0; + memcpy(memp, ptr, fp1->sz); + free(ptr); + return memp; +} + |