buffer.c

/*
 * General purpose unbounded character buffers.  This allows
 * us to buffer our scanning without arbitrary limitations
 * on any lexeme size.
 */

#include <assert.h>
#include <sys/types.h>
#include <stdlib.h>
#include "c2ada.h"


#undef NULL
#define NULL 0L

#define NEXT_INDEX(x) (((x) + 1) & (MAX_OUTBUF_LEN - 1))

static buffer_t* free_list;

static void reclaim(buffer_t* buf)
{
    buf->next = free_list;
    free_list = buf;
}

void buf_destroy(buffer_t* buf)
{
    buffer_t *next, *p;

    for(p = buf->next; p; p = next)
    {
        next = p->next;
        reclaim(p);
    }

    buf->next = NULL;
    buf->last = NULL;
    buf->head = 0;
    buf->tail = 0;
}

void buf_init(buffer_t* buf)
{
    buf->next = NULL;
    buf->last = NULL;
    buf->head = 0;
    buf->tail = 0;
}

int buf_empty(buffer_t* buf)
{
    buffer_t* next;

    if(buf == NULL)
    {
        return 1;
    }

    if(buf->head == buf->tail)
    {
        next = buf->next;
        if(next != NULL)
        {
            *buf = *next;
            if(next == buf->last)
            {
                buf->last = NULL;
            }

            reclaim(next);
            return 0;
        }

        return 1;
    }

    return 0;
}

char buf_get(buffer_t* buf)
{
    if(buf->head == buf->tail)
    {
        if(buf_empty(buf))
        {
            /* End of file */
            return 0;
        }
    }

    buf->head = NEXT_INDEX(buf->head);
    return buf->buf[buf->head];
}

static buffer_t* gen_overflow_buf()
{
    buffer_t* buf;

    if((buf = free_list))
    {
        free_list = buf->next;
    }
    else
    {
        buf = (buffer_t*)malloc(sizeof(buffer_t));
        assert(buf != NULL);
    }

    buf_init(buf);
    return buf;
}

void buf_add(buffer_t* buf, int c)
{
    int index;
    buffer_t* l;

    l = buf->last;
    if(l != NULL)
    {
        if(l->tail == (MAX_OUTBUF_LEN - 1))
        {
            l->next = gen_overflow_buf();
            buf->last = l->next;
            l = l->next;
        }

        l->tail = NEXT_INDEX(l->tail);
        l->buf[l->tail] = (char)c;
        return;
    }

    index = NEXT_INDEX(buf->tail);
    if(index == buf->head)
    {
        buf->next = gen_overflow_buf();
        l = buf->last = buf->next;
        l->buf[1] = (char)c;
        l->tail = 1;
        return;
    }

    buf->buf[index] = (char)c;
    buf->tail = index;
}

void buf_concat(buffer_t *buf, buffer_t* from_buf)
{
    char c;

    for(;;)
    {
        c = buf_get(from_buf);
        if(c == 0)
            break;
        buf_add(buf, (int)c);
    }
}

void buf_add_str(buffer_t* buf, char* str)
{
    if(str == NULL)
    {
        return;
    }

    for(; *str; str++)
    {
        buf_add(buf, (int)*str);
    }
}

int buf_count(buffer_t* buf)
{
    buffer_t* p;
    int count;

    if(buf == NULL)
    {
        return 0;
    }

    if(buf->tail >= buf->head)
    {
        count = buf->tail - buf->head;
    }
    else
    {
        count = MAX_OUTBUF_LEN - buf->head + buf->tail;
    }

    for(p = buf->next; p; p = p->next)
    {
        count += p->tail;
    }

    return count;
}

void buf_move_to(buffer_t* buf, char* str)
{
    int index = buf->head;
    int tail = buf->tail;
    buffer_t *next, *p;

    while(index != tail)
    {
        index = NEXT_INDEX(index);
        *str++ = buf->buf[index];
    }

    for(p = buf->next; p; p = next)
    {
        next = p->next;
        for(index = 1; index <= p->tail; index++)
        {
            *str++ = p->buf[index];
        }
        reclaim(p);
    }

    *str = 0;
    buf_init(buf);
}

char* buf_get_str(buffer_t* buf)
{
    int len = buf_count(buf);
    char* str;

    if(len == 0)
    {
        return NULL;
    }

    str = (char*)malloc(len + 1);
    assert(str != NULL);

    buf_move_to(buf, str);

    return str;
}