/*
 * dynstr.c - implement dynamic byte strings
 * Copyright 2010  Lars Wirzenius
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


/* We shamelessly use GNU extensions to the standard C library.
 * Primarily this is the memmem(3) function. Patches are welcome to
 * get rid of this, but I did not feel like re-inventing the wheel.
 */
#define _GNU_SOURCE

#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "dynstr.h"


/* This is how the dynamic strings are represented. */
struct Dynstr {
    unsigned char *mem;
    size_t size;
};


/* Return value for readline_helper's callback functions. */
#define DYNSTR_ERROR ((size_t) -1)


/* The current malloc and malloc error handler functions. */
static dynstr_error_handler *error_handler = dynstr_malloc_error_indicate;
static void *(*current_malloc)(size_t) = malloc;


void dynstr_init(void)
{
    error_handler = dynstr_malloc_error_indicate;
    current_malloc = malloc;
}


void *(*dynstr_get_malloc(void))(size_t)
{
    return current_malloc;
}


void dynstr_set_malloc(void *(*new_malloc)(size_t))
{
    current_malloc = new_malloc;
}


dynstr_error_handler *dynstr_get_malloc_error_handler(void)
{
    return error_handler;
}


void dynstr_set_malloc_error_handler(dynstr_error_handler *handler)
{
    error_handler = handler;
}


void dynstr_malloc_error_indicate(int error, size_t size, void *oldptr)
{
}

void dynstr_malloc_error_abort(int error, size_t size, void *oldptr)
{
    abort();
}


/* Dynamically allocate a number of bytes. Call error handler if necessary. */
static void *alloc(size_t size)
{
    void *p;
    
    p = current_malloc(size);
    if (p == NULL)
        error_handler(errno, size, NULL);
    return p;
}


static Dynstr *new_dynstr(const void *mem, size_t size, bool dynamic)
{
    Dynstr *dynstr;
    
    if (dynamic) {
        dynstr = alloc(sizeof(Dynstr) + size);
        if (dynstr == NULL)
            return NULL;
        dynstr->mem = ((unsigned char *) dynstr) + sizeof(Dynstr);
    } else {
        dynstr = alloc(sizeof(Dynstr));
        if (dynstr == NULL)
            return NULL;
        dynstr->mem = (unsigned char *) mem;
    }

    dynstr->size = size;
    return dynstr;
}


static void init_dynstr(Dynstr *dynstr, const void *mem, bool dynamic)
{
    if (dynamic)
        memcpy(dynstr->mem, mem, dynstr->size);
}


/* Allocate a new dynamic string. If dynamic is true, the contents of the
 * new string is copied from mem. Otherwise the new string just uses mem
 * directly. */
static Dynstr *newstr(const void *mem, size_t size, bool dynamic)
{
    Dynstr *dynstr;
    
    dynstr = new_dynstr(mem, size, dynamic);
    if (dynstr != NULL)
        init_dynstr(dynstr, mem, dynamic);
    return dynstr;
}


Dynstr *dynstr_new_empty(void)
{
    return new_dynstr(NULL, 0, false);
}


Dynstr *dynstr_new_from_cstring(const char *cstring)
{
    return newstr(cstring, strlen(cstring), true);
}


Dynstr *dynstr_new_from_memory(const void *mem, size_t size)
{
    return newstr(mem, size, true);
}


Dynstr *dynstr_new_from_constant_cstring(const char *cstring)
{
    return newstr(cstring, strlen(cstring), false);
}


Dynstr *dynstr_new_from_constant_memory(const void *mem, size_t size)
{
    return newstr(mem, size, false);
}


void dynstr_free(Dynstr *dynstr)
{
    free(dynstr);
}


size_t dynstr_len(Dynstr *dynstr)
{
    return dynstr->size;
}


bool dynstr_is_empty(Dynstr *dynstr)
{
    return dynstr_len(dynstr) == 0;
}


size_t dynstr_memcpy(void *mem, Dynstr *dynstr, size_t offset, size_t size)
{
    size_t len;
    
    len = dynstr_len(dynstr);
    if (offset >= len)
        return 0;
    if (size > len - offset)
        size = len - offset;
    memcpy(mem, dynstr->mem + offset, size);
    return size;
}


char *dynstr_strdup(Dynstr *dynstr)
{
    char *mem;
    
    mem = alloc(dynstr->size + 1);
    if (mem == NULL)
        return NULL;
    memcpy(mem, dynstr->mem, dynstr->size);
    mem[dynstr->size] = '\0';
    return mem;
}


Dynstr *dynstr_substr(Dynstr *dynstr, size_t offset, size_t size)
{
    if (offset >= dynstr->size) {
        offset = 0;
        size = 0;
    } else if (size > dynstr->size - offset) {
        size = dynstr->size - offset;
    }
    return newstr(dynstr->mem + offset, size, true);
}


Dynstr *dynstr_cat(Dynstr *dynstr1, Dynstr *dynstr2)
{
    return dynstr_cat_many(dynstr1, dynstr2, (Dynstr *) NULL);
}


Dynstr *dynstr_cat_many(Dynstr *dynstr, ...)
{
    va_list args;
    Dynstr *result;
    size_t size;
    size_t offset;
    
    va_start(args, dynstr);
    size = 0;
    for (Dynstr *p = dynstr; p != NULL; p = va_arg(args, Dynstr *))
        size += p->size;
    va_end(args);
    
    result = new_dynstr(NULL, size, true);
    if (result == NULL)
        return NULL;

    va_start(args, dynstr);
    offset = 0;
    for (Dynstr *p = dynstr; p != NULL; p = va_arg(args, Dynstr *)) {
        memcpy(result->mem + offset, p->mem, p->size);
        offset += p->size;
    }
    va_end(args);

    return result;
}


int dynstr_byte_at(Dynstr *dynstr, size_t offset)
{
    if (offset >= dynstr->size)
        return -1;
    return dynstr->mem[offset];
}


size_t dynstr_first_byte(Dynstr *dynstr, size_t offset, int byte)
{
    unsigned char *p;

    if (offset >= dynstr->size)
        return DYNSTR_NOT_FOUND;
    p = memchr(dynstr->mem + offset, byte, dynstr->size - offset);
    if (p == NULL)
        return DYNSTR_NOT_FOUND;
    return (size_t) (p - dynstr->mem);
}


size_t dynstr_last_byte(Dynstr *dynstr, size_t offset, int byte)
{
    unsigned char *p;

    if (offset >= dynstr->size)
        return DYNSTR_NOT_FOUND;
    p = memrchr(dynstr->mem + offset, byte, dynstr->size - offset);
    if (p == NULL)
        return DYNSTR_NOT_FOUND;
    return (size_t) (p - dynstr->mem);
}


size_t dynstr_first_string(Dynstr *dynstr, size_t offset, Dynstr *pattern)
{
    const unsigned char *p;
    
    if (offset >= dynstr->size)
        return DYNSTR_NOT_FOUND;
    if (pattern->size == 0)
        return DYNSTR_NOT_FOUND;
    p = memmem(dynstr->mem + offset, dynstr->size - offset, 
               pattern->mem, pattern->size);
    if (p == NULL)
        return DYNSTR_NOT_FOUND;
    return (size_t) (p - dynstr->mem);
}


size_t dynstr_last_string(Dynstr *dynstr, size_t offset, Dynstr *pattern)
{
    size_t result;
    size_t new_result;

    /* GNU libc lacks a memrmem function, so we loop to the last
     * dynstr_first_string match. */
    result = DYNSTR_NOT_FOUND;    
    for (;;) {
        new_result = dynstr_first_string(dynstr, offset, pattern);
        if (new_result == DYNSTR_NOT_FOUND)
            break;
        result = new_result;
        offset = result + 1;
    }
    return result;
}


int dynstr_cmp(Dynstr *dynstr1, Dynstr *dynstr2)
{
    int result;
    size_t min_size;

    if (dynstr1->size < dynstr2->size)
        min_size = dynstr1->size;
    else
        min_size = dynstr2->size;
    result = memcmp(dynstr1->mem, dynstr2->mem, min_size);
    if (result == 0) {
        if (dynstr1->size < dynstr2->size)
            return -1;
        else if (dynstr1->size == dynstr2->size)
            return 0;
        else
            return 1;
    }
    return result;
}


size_t dynstr_fwrite(FILE *file, Dynstr *dynstr)
{
    return fwrite(dynstr->mem, 1, dynstr->size, file);
}


ssize_t dynstr_write(int fd, Dynstr *dynstr)
{
    return write(fd, dynstr->mem, dynstr->size);
}


/* A helper function for dynstr_read and dynstr_fread. The callback does
 * the actual reading. */
static Dynstr *read_helper(size_t (*callback)(FILE *f, int fd, unsigned char *buf,
                                              size_t size),
                           FILE *f, int fd, size_t size)
{
    Dynstr *dynstr;
    Dynstr *dynstr2;
    size_t n;
    
    dynstr = new_dynstr(NULL, size, true);
    if (dynstr == NULL)
        return NULL;

    n = callback(f, fd, dynstr->mem, size);
    if (n == DYNSTR_ERROR) {
        int saved = errno;
        dynstr_free(dynstr);
        errno = saved;
        return NULL;
    }
    
    if (n < size) {
        dynstr2 = dynstr_substr(dynstr, 0, n);
        if (dynstr2 == NULL) {
            dynstr->size = n;
        } else {
            dynstr_free(dynstr);
            dynstr = dynstr2;
        }
    }

    return dynstr;
}


static size_t fread_callback(FILE *f, int fd, unsigned char *buf, size_t size)
{
    size_t n;
    
    n = fread(buf, 1, size, f);
    if (n == 0 && ferror(f))
        return DYNSTR_ERROR;
    return n;
}


static size_t read_callback(FILE *f, int fd, unsigned char *buf, size_t size)
{
    ssize_t n;

    do {
        n = read(fd, buf, size);
    } while (n == -1 && errno == EINTR);
    if (n == -1)
        return DYNSTR_ERROR;
    return n;
}


Dynstr *dynstr_fread(FILE *file, size_t size)
{
    return read_helper(fread_callback, file, -1, size);
}


Dynstr *dynstr_read(int file, size_t size)
{
    return read_helper(read_callback, NULL, file, size);
}


/* Helper function for dynstr_readline and dynstr_freadline. The callback
 * does the actual reading. Reading happens one byte at a time, since we
 * must not read past the newline that terminates a line. */
static Dynstr *readline_helper(int (*callback)(FILE *, int), FILE *f, int fd)
{
    Dynstr *line;
    Dynstr *temp1;
    Dynstr *temp2;
    int c;
    unsigned char buf[1024];
    size_t buflen;
    int saved;
    
    line = dynstr_new_empty();
    buflen = 0;

    for (;;) {
        temp1 = NULL;
        temp2 = NULL;

        c = callback(f, fd);
        if (c == -1)
            goto error;
        else if (c == -2)
            break;

        buf[buflen++] = c;
        if (buflen == sizeof(buf)) {
            temp1 = dynstr_new_from_constant_memory(buf, buflen);
            if (temp1 == NULL)
                goto error;
            temp2 = dynstr_cat(line, temp1);
            if (temp2 == NULL)
                goto error;
            dynstr_free(temp1);
            dynstr_free(line);
            line = temp2;
            buflen = 0;
        }

        if (c == '\n')
            break;
    }
    
    if (buflen > 0) {
        temp1 = dynstr_new_from_constant_memory(buf, buflen);
        if (temp1 == NULL)
            goto error;
        temp2 = dynstr_cat(line, temp1);
        if (temp2 == NULL)
            goto error;
        dynstr_free(temp1);
        dynstr_free(line);
        line = temp2;
    }

    return line;

error:
    saved = errno;
    dynstr_free(line);
    dynstr_free(temp1);
    dynstr_free(temp2);
    errno = saved;
    return NULL;
}


static int freadline_callback(FILE *f, int fd)
{
    int c;
    
    c = getc(f);
    if (c == EOF && ferror(f))
        return -1;
    else if (c == EOF)
        return -2;
    else
        return c;
}


Dynstr *dynstr_freadline(FILE *file)
{
    return readline_helper(freadline_callback, file, -1);
}


static int readline_callback(FILE *f, int fd)
{
    unsigned char c;
    int n;

    do {
        n = read(fd, &c, 1);
    } while (n == -1 && errno == EINTR);
    if (n == 0)
        return -2;
    else if (n == -1)
        return -1;
    else
        return c;
}


Dynstr *dynstr_readline(int file)
{
    return readline_helper(readline_callback, NULL, file);
}