/*
 * Copyright (C) 1989 by Kenneth Almquist.  All rights reserved.
 * This file is part of ash, which is distributed under the terms specified
 * by the Ash General Public License.  See the file named LICENSE.
 */

#include "shell.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "machdep.h"
#include "mystring.h"



/*
 * Like malloc, but returns an error when out of space.
 */

pointer
ckmalloc(nbytes) {
      register pointer p;
      pointer malloc();

      if ((p = malloc(nbytes)) == NULL)
	    error("Out of space");
      return p;
}


/*
 * Same for realloc.
 */

pointer
ckrealloc(p, nbytes)
      register pointer p;
      {
      pointer realloc();

      if ((p = realloc(p, nbytes)) == NULL)
	    error("Out of space");
      return p;
}


/*
 * Make a copy of a string in safe storage.
 */

char *
savestr(s)
      char *s;
      {
      register char *p;

      p = ckmalloc(strlen(s) + 1);
      scopy(s, p);
      return p;
}


/*
 * Parse trees for commands are allocated in lifo order, so we use a stack
 * to make this more efficient, and also to avoid all sorts of exception
 * handling code to handle interrupts in the middle of a parse.
 *
 * The size 504 was chosen because the Ultrix malloc handles that size
 * well.
 */

#define MINSIZE 504		/* minimum size of a block */


struct stack_block {
      struct stack_block *prev;
      char space[MINSIZE];
};

struct stack_block stackbase;
struct stack_block *stackp = &stackbase;
char *stacknxt = stackbase.space;
int stacknleft = MINSIZE;
int sstrnleft;
int herefd = -1;



pointer
stalloc(nbytes) {
      register char *p;

      nbytes = ALIGN(nbytes);
      if (nbytes > stacknleft) {
	    int blocksize;
	    struct stack_block *sp;

	    blocksize = nbytes;
	    if (blocksize < MINSIZE)
		  blocksize = MINSIZE;
	    INTOFF;
	    sp = ckmalloc(sizeof(struct stack_block) - MINSIZE + blocksize);
	    sp->prev = stackp;
	    stacknxt = sp->space;
	    stacknleft = blocksize;
	    stackp = sp;
	    INTON;
      }
      p = stacknxt;
      stacknxt += nbytes;
      stacknleft -= nbytes;
      return p;
}


void
stunalloc(p)
      pointer p;
      {
      if (p == NULL) {		/*DEBUG */
	    write(2, "stunalloc\n", 10);
	    abort();
      }
      stacknleft += stacknxt - (char *)p;
      stacknxt = p;
}



void
setstackmark(mark)
      struct stackmark *mark;
      {
      mark->stackp = stackp;
      mark->stacknxt = stacknxt;
      mark->stacknleft = stacknleft;
}


void
popstackmark(mark)
      struct stackmark *mark;
      {
      struct stack_block *sp;

      INTOFF;
      while (stackp != mark->stackp) {
	    sp = stackp;
	    stackp = sp->prev;
	    ckfree(sp);
      }
      stacknxt = mark->stacknxt;
      stacknleft = mark->stacknleft;
      INTON;
}


/*
 * When the parser reads in a string, it wants to stick the string on the
 * stack and only adjust the stack pointer when it knows how big the
 * string is.  Stackblock (defined in stack.h) returns a pointer to a block
 * of space on top of the stack and stackblocklen returns the length of
 * this block.  Growstackblock will grow this space by at least one byte,
 * possibly moving it (like realloc).  Grabstackblock actually allocates the
 * part of the block that has been used.
 */

void
growstackblock() {
      char *p;
      int newlen = stacknleft * 2 + 100;
      char *oldspace = stacknxt;
      int oldlen = stacknleft;
      struct stack_block *sp;

      if (stacknxt == stackp->space && stackp != &stackbase) {
	    INTOFF;
	    sp = stackp;
	    stackp = sp->prev;
	    sp = ckrealloc((pointer)sp, sizeof(struct stack_block) - MINSIZE + newlen);
	    sp->prev = stackp;
	    stackp = sp;
	    stacknxt = sp->space;
	    stacknleft = newlen;
	    INTON;
      } else {
	    p = stalloc(newlen);
	    bcopy(oldspace, p, oldlen);
	    stacknxt = p;			/* free the space */
	    stacknleft += newlen;		/* we just allocated */
      }
}



void
grabstackblock(len) {
      len = ALIGN(len);
      stacknxt += len;
      stacknleft -= len;
}



/*
 * The following routines are somewhat easier to use that the above.
 * The user declares a variable of type STACKSTR, which may be declared
 * to be a register.  The macro STARTSTACKSTR initializes things.  Then
 * the user uses the macro STPUTC to add characters to the string.  In
 * effect, STPUTC(c, p) is the same as *p++ = c except that the stack is
 * grown as necessary.  When the user is done, she can just leave the
 * string there and refer to it using stackblock().  Or she can allocate
 * the space for it using grabstackstr().  If it is necessary to allow
 * someone else to use the stack temporarily and then continue to grow
 * the string, the user should use grabstack to allocate the space, and
 * then call ungrabstr(p) to return to the previous mode of operation.
 *
 * USTPUTC is like STPUTC except that it doesn't check for overflow.
 * CHECKSTACKSPACE can be called before USTPUTC to ensure that there
 * is space for at least one character.
 */


char *
growstackstr() {
      int len = stackblocksize();
      if (herefd >= 0 && len >= 1024) {
	    xwrite(herefd, stackblock(), len);
	    sstrnleft = len - 1;
	    return stackblock();
      }
      growstackblock();
      sstrnleft = stackblocksize() - len - 1;
      return stackblock() + len;
}


/*
 * Called from CHECKSTRSPACE.
 */

char *
makestrspace() {
      int len = stackblocksize() - sstrnleft;
      growstackblock();
      sstrnleft = stackblocksize() - len;
      return stackblock() + len;
}



void
ungrabstackstr(s, p)
      char *s;
      char *p;
      {
      stacknleft += stacknxt - s;
      stacknxt = s;
      sstrnleft = stacknleft - (p - s);
}