/* -*- mode: c; indent-tabs-mode: nil -*- */
/* Coding Buffer Implementation */

/*
  Implementation

    Encoding mode

    The encoding buffer is filled from bottom (lowest address) to top
    (highest address).  This makes it easier to expand the buffer,
    since realloc preserves the existing portion of the buffer.

    Note: Since ASN.1 encoding must be done in reverse, this means
    that you can't simply memcpy out the buffer data, since it will be
    backwards.  You need to reverse-iterate through it, instead.

    ***This decision may have been a mistake.  In practice, the
    implementation will probably be tuned such that reallocation is
    rarely necessary.  Also, the realloc probably has recopy the
    buffer itself, so we don't really gain that much by avoiding an
    explicit copy of the buffer.  --Keep this in mind for future reference.


    Decoding mode

    The decoding buffer is in normal order and is created by wrapping
    an asn1buf around a krb5_data structure.
  */

/* Abstraction Function

   Programs should use just pointers to asn1buf's (e.g. asn1buf *mybuf).
   These pointers must always point to a valid, allocated asn1buf
   structure or be NULL.

   The contents of the asn1buf represent an octet string.  This string
   begins at base and continues to the octet immediately preceding next.
   If next == base or mybuf == NULL, then the asn1buf represents an empty
   octet string. */

/* Representation Invariant

   Pointers to asn1buf's must always point to a valid, allocated
   asn1buf structure or be NULL.

   base points to a valid, allocated octet array or is NULL
   bound, if non-NULL, points to the last valid octet
   next >= base
   next <= bound+2  (i.e. next should be able to step just past the bound,
                     but no further.  (The bound should move out in response
                     to being crossed by next.)) */

#define ASN1BUF_OMIT_INLINE_FUNCS
#include "asn1buf.h"
#include <stdio.h>
#include "asn1_get.h"

#ifdef USE_VALGRIND
#include <valgrind/memcheck.h>
#else
#define VALGRIND_CHECK_READABLE(PTR,SIZE) ((void)0)
#endif

#if !defined(__GNUC__) || defined(CONFIG_SMALL)
/* Declare private procedures as static if they're not used for inline
   expansion of other stuff elsewhere.  */
static unsigned int asn1buf_free(const asn1buf *);
static asn1_error_code asn1buf_ensure_space(asn1buf *, unsigned int);
static asn1_error_code asn1buf_expand(asn1buf *, unsigned int);
#endif

#define asn1_is_eoc(class, num, indef)  \
((class) == UNIVERSAL && !(num) && !(indef))

asn1_error_code asn1buf_create(asn1buf **buf)
{
    *buf = (asn1buf*)malloc(sizeof(asn1buf));
    if (*buf == NULL) return ENOMEM;
    (*buf)->base = NULL;
    (*buf)->bound = NULL;
    (*buf)->next = NULL;
    return 0;
}

asn1_error_code asn1buf_wrap_data(asn1buf *buf, const krb5_data *code)
{
    if (code == NULL || code->data == NULL) return ASN1_MISSING_FIELD;
    buf->next = buf->base = code->data;
    buf->bound = code->data + code->length - 1;
    return 0;
}

asn1_error_code asn1buf_imbed(asn1buf *subbuf, const asn1buf *buf, const unsigned int length, const int indef)
{
    subbuf->base = subbuf->next = buf->next;
    if (!indef) {
        subbuf->bound = subbuf->base + length - 1;
        if (subbuf->bound > buf->bound)
            return ASN1_OVERRUN;
    } else /* constructed indefinite */
        subbuf->bound = buf->bound;
    return 0;
}

asn1_error_code asn1buf_sync(asn1buf *buf, asn1buf *subbuf,
                             asn1_class asn1class, asn1_tagnum lasttag,
                             unsigned int length, int indef, int seqindef)
{
    asn1_error_code retval;

    if (!seqindef) {
        /* sequence was encoded as definite length */
        buf->next = subbuf->bound + 1;
    } else if (!asn1_is_eoc(asn1class, lasttag, indef)) {
        retval = asn1buf_skiptail(subbuf, length, indef);
        if (retval)
            return retval;
    } else {
        /* We have just read the EOC octets. */
        buf->next = subbuf->next;
    }
    return 0;
}

asn1_error_code asn1buf_skiptail(asn1buf *buf, const unsigned int length, const int indef)
{
    asn1_error_code retval;
    taginfo t;
    int nestlevel;

    nestlevel = 1 + indef;
    if (!indef) {
        if (length <= (size_t)(buf->bound - buf->next + 1))
            buf->next += length;
        else
            return ASN1_OVERRUN;
    }
    while (nestlevel > 0) {
        if (buf->bound - buf->next + 1 <= 0)
            return ASN1_OVERRUN;
        retval = asn1_get_tag_2(buf, &t);
        if (retval) return retval;
        if (!t.indef) {
            if (t.length <= (size_t)(buf->bound - buf->next + 1))
                buf->next += t.length;
            else
                return ASN1_OVERRUN;
        }
        if (t.indef)
            nestlevel++;
        if (asn1_is_eoc(t.asn1class, t.tagnum, t.indef))
            nestlevel--;                /* got an EOC encoding */
    }
    return 0;
}

void asn1buf_destroy(asn1buf **buf)
{
    if (*buf != NULL) {
        free((*buf)->base);
        free(*buf);
        *buf = NULL;
    }
}

#ifdef asn1buf_insert_octet
#undef asn1buf_insert_octet
#endif
asn1_error_code asn1buf_insert_octet(asn1buf *buf, const int o)
{
    asn1_error_code retval;

    retval = asn1buf_ensure_space(buf,1U);
    if (retval) return retval;
    *(buf->next) = (char)o;
    (buf->next)++;
    return 0;
}

asn1_error_code
asn1buf_insert_bytestring(asn1buf *buf, const unsigned int len, const void *sv)
{
    asn1_error_code retval;
    unsigned int length;
    const char *s = sv;

    retval = asn1buf_ensure_space(buf,len);
    if (retval) return retval;
    VALGRIND_CHECK_READABLE(sv, len);
    for (length=1; length<=len; length++,(buf->next)++)
        *(buf->next) = (s[len-length]);
    return 0;
}


#undef asn1buf_remove_octet
asn1_error_code asn1buf_remove_octet(asn1buf *buf, asn1_octet *o)
{
    if (buf->next > buf->bound) return ASN1_OVERRUN;
    *o = (asn1_octet)(*((buf->next)++));
    return 0;
}

asn1_error_code asn1buf_remove_octetstring(asn1buf *buf, const unsigned int len, asn1_octet **s)
{
    unsigned int i;

    if (len > (size_t)(buf->bound + 1 - buf->next)) return ASN1_OVERRUN;
    if (len == 0) {
        *s = 0;
        return 0;
    }
    *s = (asn1_octet*)malloc(len*sizeof(asn1_octet));
    if (*s == NULL)
        return ENOMEM;
    for (i=0; i<len; i++)
        (*s)[i] = (asn1_octet)(buf->next)[i];
    buf->next += len;
    return 0;
}

asn1_error_code asn1buf_remove_charstring(asn1buf *buf, const unsigned int len, char **s)
{
    unsigned int i;

    if (len > (size_t)(buf->bound + 1 - buf->next)) return ASN1_OVERRUN;
    if (len == 0) {
        *s = 0;
        return 0;
    }
    *s = (char*)malloc(len*sizeof(char));
    if (*s == NULL) return ENOMEM;
    for (i=0; i<len; i++)
        (*s)[i] = (char)(buf->next)[i];
    buf->next += len;
    return 0;
}

int asn1buf_remains(asn1buf *buf, int indef)
{
    int remain;
    if (buf == NULL || buf->base == NULL) return 0;
    remain = buf->bound - buf->next +1;
    if (remain <= 0) return remain;
    /*
     * Two 0 octets means the end of an indefinite encoding.
     */
    if (indef && remain >= 2 && !*(buf->next) && !*(buf->next + 1))
        return 0;
    else return remain;
}

asn1_error_code asn12krb5_buf(const asn1buf *buf, krb5_data **code)
{
    unsigned int i;
    krb5_data *d;

    *code = NULL;

    d = calloc(1, sizeof(krb5_data));
    if (d == NULL)
        return ENOMEM;
    d->length = asn1buf_len(buf);
    d->data = malloc(d->length + 1);
    if (d->data == NULL) {
        free(d);
        return ENOMEM;
    }
    for (i=0; i < d->length; i++)
        d->data[i] = buf->base[d->length - i - 1];
    d->data[d->length] = '\0';
    d->magic = KV5M_DATA;
    *code = d;
    return 0;
}



/* These parse and unparse procedures should be moved out. They're
   useful only for debugging and superfluous in the production version. */

asn1_error_code asn1buf_unparse(const asn1buf *buf, char **s)
{
    free(*s);
    if (buf == NULL) {
        *s = strdup("<NULL>");
        if (*s == NULL) return ENOMEM;
    } else if (buf->base == NULL) {
        *s = strdup("<EMPTY>");
        if (*s == NULL) return ENOMEM;
    } else {
        unsigned int length = asn1buf_len(buf);
        unsigned int i;

        *s = calloc(length+1, sizeof(char));
        if (*s == NULL) return ENOMEM;
        (*s)[length] = '\0';
        for (i=0; i<length; i++) ;
/*      OLDDECLARG( (*s)[i] = , (buf->base)[length-i-1]) */
    }
    return 0;
}

asn1_error_code asn1buf_hex_unparse(const asn1buf *buf, char **s)
{
#define hexchar(d) ((d)<=9 ? ('0'+(d)) :        \
                    ((d)<=15 ? ('A'+(d)-10) :   \
                     'X'))

    free(*s);

    if (buf == NULL) {
        *s = strdup("<NULL>");
        if (*s == NULL) return ENOMEM;
    } else if (buf->base == NULL) {
        *s = strdup("<EMPTY>");
        if (*s == NULL) return ENOMEM;
    } else {
        unsigned int length = asn1buf_len(buf);
        int i;

        *s = malloc(3*length);
        if (*s == NULL) return ENOMEM;
        for (i = length-1; i >= 0; i--) {
            (*s)[3*(length-i-1)] = hexchar(((buf->base)[i]&0xF0)>>4);
            (*s)[3*(length-i-1)+1] = hexchar((buf->base)[i]&0x0F);
            (*s)[3*(length-i-1)+2] = ' ';
        }
        (*s)[3*length-1] = '\0';
    }
    return 0;
}

/****************************************************************/
/* Private Procedures */

static int asn1buf_size(const asn1buf *buf)
{
    if (buf == NULL || buf->base == NULL) return 0;
    return buf->bound - buf->base + 1;
}

#undef asn1buf_free
unsigned int asn1buf_free(const asn1buf *buf)
{
    if (buf == NULL || buf->base == NULL) return 0;
    else return buf->bound - buf->next + 1;
}

#undef asn1buf_ensure_space
asn1_error_code asn1buf_ensure_space(asn1buf *buf, const unsigned int amount)
{
    unsigned int avail = asn1buf_free(buf);
    if (avail >= amount)
        return 0;
    return asn1buf_expand(buf, amount-avail);
}

asn1_error_code asn1buf_expand(asn1buf *buf, unsigned int inc)
{
#define STANDARD_INCREMENT 200
    int next_offset = buf->next - buf->base;
    int bound_offset;
    if (buf->base == NULL) bound_offset = -1;
    else bound_offset = buf->bound - buf->base;

    if (inc < STANDARD_INCREMENT)
        inc = STANDARD_INCREMENT;

    buf->base = realloc(buf->base,
                        (asn1buf_size(buf)+inc) * sizeof(asn1_octet));
    if (buf->base == NULL) return ENOMEM; /* XXX leak */
    buf->bound = (buf->base) + bound_offset + inc;
    buf->next = (buf->base) + next_offset;
    return 0;
}

#undef asn1buf_len
int asn1buf_len(const asn1buf *buf)
{
    return buf->next - buf->base;
}