xref: /unit/src/nxt_conf.c (revision 2139:99d792169ffb)

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Valentin V. Bartenev
 * Copyright (C) NGINX, Inc.
 */

#include <nxt_main.h>
#include <nxt_conf.h>

#include <float.h>
#include <math.h>


#define NXT_CONF_MAX_SHORT_STRING  14
#define NXT_CONF_MAX_NUMBER_LEN    14
#define NXT_CONF_MAX_STRING        NXT_INT32_T_MAX

#define NXT_CONF_MAX_TOKEN_LEN     256


typedef enum {
    NXT_CONF_VALUE_NULL = 0,
    NXT_CONF_VALUE_BOOLEAN,
    NXT_CONF_VALUE_INTEGER,
    NXT_CONF_VALUE_NUMBER,
    NXT_CONF_VALUE_SHORT_STRING,
    NXT_CONF_VALUE_STRING,
    NXT_CONF_VALUE_ARRAY,
    NXT_CONF_VALUE_OBJECT,
} nxt_conf_value_type_t;


typedef enum {
    NXT_CONF_OP_PASS = 0,
    NXT_CONF_OP_CREATE,
    NXT_CONF_OP_REPLACE,
    NXT_CONF_OP_DELETE,
} nxt_conf_op_action_t;


typedef struct nxt_conf_array_s   nxt_conf_array_t;
typedef struct nxt_conf_object_s  nxt_conf_object_t;


struct nxt_conf_value_s {
    union {
        uint8_t               boolean;  /* 1 bit. */
        u_char                number[NXT_CONF_MAX_NUMBER_LEN + 1];;

        struct {
            u_char            start[NXT_CONF_MAX_SHORT_STRING];
            uint8_t           length;
        } str;

        struct {
            u_char            *start;
            uint32_t          length;
        } nxt_packed string;

        nxt_conf_array_t      *array;
        nxt_conf_object_t     *object;
    } nxt_packed u;

    uint8_t                   type;  /* 3 bits. */
} nxt_aligned(8);


struct nxt_conf_array_s {
    nxt_uint_t                count;
    nxt_conf_value_t          elements[];
};


typedef struct {
    nxt_conf_value_t          name;
    nxt_conf_value_t          value;
} nxt_conf_object_member_t;


struct nxt_conf_object_s {
    nxt_uint_t                count;
    nxt_conf_object_member_t  members[];
};


struct nxt_conf_op_s {
    uint32_t                  index;
    uint32_t                  action;  /* nxt_conf_op_action_t */
    void                      *ctx;
};


typedef struct {
    u_char                    *start;
    u_char                    *end;
    nxt_bool_t                last;
    u_char                    buf[NXT_CONF_MAX_TOKEN_LEN];
} nxt_conf_path_parse_t;


static nxt_int_t nxt_conf_path_next_token(nxt_conf_path_parse_t *parse,
    nxt_str_t *token);

static u_char *nxt_conf_json_skip_space(u_char *start, const u_char *end);
static u_char *nxt_conf_json_parse_value(nxt_mp_t *mp, nxt_conf_value_t *value,
    u_char *start, u_char *end, nxt_conf_json_error_t *error);
static u_char *nxt_conf_json_parse_object(nxt_mp_t *mp, nxt_conf_value_t *value,
    u_char *start, u_char *end, nxt_conf_json_error_t *error);
static nxt_int_t nxt_conf_object_hash_add(nxt_mp_t *mp,
    nxt_lvlhsh_t *lvlhsh, nxt_conf_object_member_t *member);
static nxt_int_t nxt_conf_object_hash_test(nxt_lvlhsh_query_t *lhq,
    void *data);
static void *nxt_conf_object_hash_alloc(void *data, size_t size);
static void nxt_conf_object_hash_free(void *data, void *p);
static u_char *nxt_conf_json_parse_array(nxt_mp_t *mp, nxt_conf_value_t *value,
    u_char *start, u_char *end, nxt_conf_json_error_t *error);
static u_char *nxt_conf_json_parse_string(nxt_mp_t *mp, nxt_conf_value_t *value,
    u_char *start, u_char *end, nxt_conf_json_error_t *error);
static u_char *nxt_conf_json_parse_number(nxt_mp_t *mp, nxt_conf_value_t *value,
    u_char *start, u_char *end, nxt_conf_json_error_t *error);
static void nxt_conf_json_parse_error(nxt_conf_json_error_t *error, u_char *pos,
    const char *detail);

static nxt_int_t nxt_conf_copy_value(nxt_mp_t *mp, nxt_conf_op_t *op,
    nxt_conf_value_t *dst, nxt_conf_value_t *src);
static nxt_int_t nxt_conf_copy_array(nxt_mp_t *mp, nxt_conf_op_t *op,
    nxt_conf_value_t *dst, nxt_conf_value_t *src);
static nxt_int_t nxt_conf_copy_object(nxt_mp_t *mp, nxt_conf_op_t *op,
    nxt_conf_value_t *dst, nxt_conf_value_t *src);

static size_t nxt_conf_json_string_length(nxt_conf_value_t *value);
static u_char *nxt_conf_json_print_string(u_char *p, nxt_conf_value_t *value);
static size_t nxt_conf_json_array_length(nxt_conf_value_t *value,
    nxt_conf_json_pretty_t *pretty);
static u_char *nxt_conf_json_print_array(u_char *p, nxt_conf_value_t *value,
    nxt_conf_json_pretty_t *pretty);
static size_t nxt_conf_json_object_length(nxt_conf_value_t *value,
    nxt_conf_json_pretty_t *pretty);
static u_char *nxt_conf_json_print_object(u_char *p, nxt_conf_value_t *value,
    nxt_conf_json_pretty_t *pretty);

static size_t nxt_conf_json_escape_length(u_char *p, size_t size);
static u_char *nxt_conf_json_escape(u_char *dst, u_char *src, size_t size);


#define nxt_conf_json_newline(p)                                              \
    ((p)[0] = '\r', (p)[1] = '\n', (p) + 2)


nxt_inline u_char *
nxt_conf_json_indentation(u_char *p, uint32_t level)
{
    while (level) {
        *p++ = '\t';
        level--;
    }

    return p;
}


void
nxt_conf_get_string(nxt_conf_value_t *value, nxt_str_t *str)
{
    if (value->type == NXT_CONF_VALUE_SHORT_STRING) {
        str->length = value->u.str.length;
        str->start = value->u.str.start;

    } else {
        str->length = value->u.string.length;
        str->start = value->u.string.start;
    }
}


void
nxt_conf_set_string(nxt_conf_value_t *value, nxt_str_t *str)
{
    if (str->length > NXT_CONF_MAX_SHORT_STRING) {
        value->type = NXT_CONF_VALUE_STRING;
        value->u.string.length = str->length;
        value->u.string.start = str->start;

    } else {
        value->type = NXT_CONF_VALUE_SHORT_STRING;
        value->u.str.length = str->length;

        nxt_memcpy(value->u.str.start, str->start, str->length);
    }
}


nxt_int_t
nxt_conf_set_string_dup(nxt_conf_value_t *value, nxt_mp_t *mp,
    const nxt_str_t *str)
{
    nxt_str_t  tmp, *ptr;

    if (str->length > NXT_CONF_MAX_SHORT_STRING) {
        value->type = NXT_CONF_VALUE_STRING;

        ptr = nxt_str_dup(mp, &tmp, str);
        if (nxt_slow_path(ptr == NULL)) {
            return NXT_ERROR;
        }

        value->u.string.length = tmp.length;
        value->u.string.start = tmp.start;

    } else {
        value->type = NXT_CONF_VALUE_SHORT_STRING;
        value->u.str.length = str->length;

        nxt_memcpy(value->u.str.start, str->start, str->length);
    }

    return NXT_OK;
}


double
nxt_conf_get_number(nxt_conf_value_t *value)
{
    return nxt_strtod(value->u.number, NULL);
}


uint8_t
nxt_conf_get_boolean(nxt_conf_value_t *value)
{
    return value->u.boolean;
}


nxt_uint_t
nxt_conf_object_members_count(nxt_conf_value_t *value)
{
    return value->u.object->count;
}


nxt_conf_value_t *
nxt_conf_create_object(nxt_mp_t *mp, nxt_uint_t count)
{
    size_t            size;
    nxt_conf_value_t  *value;

    size = sizeof(nxt_conf_value_t)
           + sizeof(nxt_conf_object_t)
           + count * sizeof(nxt_conf_object_member_t);

    value = nxt_mp_get(mp, size);
    if (nxt_slow_path(value == NULL)) {
        return NULL;
    }

    value->u.object = nxt_pointer_to(value, sizeof(nxt_conf_value_t));
    value->u.object->count = count;

    value->type = NXT_CONF_VALUE_OBJECT;

    return value;
}


void
nxt_conf_set_member(nxt_conf_value_t *object, nxt_str_t *name,
    const nxt_conf_value_t *value, uint32_t index)
{
    nxt_conf_object_member_t  *member;

    member = &object->u.object->members[index];

    nxt_conf_set_string(&member->name, name);

    member->value = *value;
}


void
nxt_conf_set_member_string(nxt_conf_value_t *object, nxt_str_t *name,
    nxt_str_t *value, uint32_t index)
{
    nxt_conf_object_member_t  *member;

    member = &object->u.object->members[index];

    nxt_conf_set_string(&member->name, name);

    nxt_conf_set_string(&member->value, value);
}


nxt_int_t
nxt_conf_set_member_string_dup(nxt_conf_value_t *object, nxt_mp_t *mp,
    nxt_str_t *name, nxt_str_t *value, uint32_t index)
{
    nxt_conf_object_member_t  *member;

    member = &object->u.object->members[index];

    nxt_conf_set_string(&member->name, name);

    return nxt_conf_set_string_dup(&member->value, mp, value);
}


void
nxt_conf_set_member_integer(nxt_conf_value_t *object, nxt_str_t *name,
    int64_t value, uint32_t index)
{
    u_char                    *p, *end;
    nxt_conf_object_member_t  *member;

    member = &object->u.object->members[index];

    nxt_conf_set_string(&member->name, name);

    p = member->value.u.number;
    end = p + NXT_CONF_MAX_NUMBER_LEN;

    end = nxt_sprintf(p, end, "%L", value);
    *end = '\0';

    member->value.type = NXT_CONF_VALUE_INTEGER;
}


void
nxt_conf_set_member_null(nxt_conf_value_t *object, nxt_str_t *name,
    uint32_t index)
{
    nxt_conf_object_member_t  *member;

    member = &object->u.object->members[index];

    nxt_conf_set_string(&member->name, name);

    member->value.type = NXT_CONF_VALUE_NULL;
}


nxt_conf_value_t *
nxt_conf_create_array(nxt_mp_t *mp, nxt_uint_t count)
{
    size_t            size;
    nxt_conf_value_t  *value;

    size = sizeof(nxt_conf_value_t)
           + sizeof(nxt_conf_array_t)
           + count * sizeof(nxt_conf_value_t);

    value = nxt_mp_get(mp, size);
    if (nxt_slow_path(value == NULL)) {
        return NULL;
    }

    value->u.array = nxt_pointer_to(value, sizeof(nxt_conf_value_t));
    value->u.array->count = count;

    value->type = NXT_CONF_VALUE_ARRAY;

    return value;
}


void
nxt_conf_set_element(nxt_conf_value_t *array, nxt_uint_t index,
    const nxt_conf_value_t *value)
{
    array->u.array->elements[index] = *value;
}


nxt_int_t
nxt_conf_set_element_string_dup(nxt_conf_value_t *array, nxt_mp_t *mp,
    nxt_uint_t index, nxt_str_t *value)
{
    nxt_conf_value_t  *element;

    element = &array->u.array->elements[index];

    return nxt_conf_set_string_dup(element, mp, value);
}


nxt_uint_t
nxt_conf_array_elements_count(nxt_conf_value_t *value)
{
    return value->u.array->count;
}


nxt_uint_t
nxt_conf_array_elements_count_or_1(nxt_conf_value_t *value)
{
    return (value->type == NXT_CONF_VALUE_ARRAY) ? value->u.array->count : 1;
}


nxt_uint_t
nxt_conf_type(nxt_conf_value_t *value)
{
    switch (value->type) {

    case NXT_CONF_VALUE_NULL:
        return NXT_CONF_NULL;

    case NXT_CONF_VALUE_BOOLEAN:
        return NXT_CONF_BOOLEAN;

    case NXT_CONF_VALUE_INTEGER:
        return NXT_CONF_INTEGER;

    case NXT_CONF_VALUE_NUMBER:
        return NXT_CONF_NUMBER;

    case NXT_CONF_VALUE_SHORT_STRING:
    case NXT_CONF_VALUE_STRING:
        return NXT_CONF_STRING;

    case NXT_CONF_VALUE_ARRAY:
        return NXT_CONF_ARRAY;

    case NXT_CONF_VALUE_OBJECT:
        return NXT_CONF_OBJECT;
    }

    nxt_unreachable();

    return 0;
}


nxt_conf_value_t *
nxt_conf_get_path(nxt_conf_value_t *value, nxt_str_t *path)
{
    nxt_str_t              token;
    nxt_int_t              ret, index;
    nxt_conf_path_parse_t  parse;

    parse.start = path->start;
    parse.end = path->start + path->length;
    parse.last = 0;

    do {
        ret = nxt_conf_path_next_token(&parse, &token);
        if (nxt_slow_path(ret != NXT_OK)) {
            return NULL;
        }

        if (token.length == 0) {

            if (parse.last) {
                break;
            }

            return NULL;
        }

        switch (value->type) {

        case NXT_CONF_VALUE_OBJECT:
            value = nxt_conf_get_object_member(value, &token, NULL);
            break;

        case NXT_CONF_VALUE_ARRAY:
            index = nxt_int_parse(token.start, token.length);

            if (index < 0 || index > NXT_INT32_T_MAX) {
                return NULL;
            }

            value = nxt_conf_get_array_element(value, index);
            break;

        default:
            return NULL;
        }

        if (value == NULL) {
            return NULL;
        }

    } while (parse.last == 0);

    return value;
}


static nxt_int_t
nxt_conf_path_next_token(nxt_conf_path_parse_t *parse, nxt_str_t *token)
{
    u_char  *p, *start, *end;
    size_t  length;

    start = parse->start + 1;

    p = start;

    while (p < parse->end && *p != '/') {
        p++;
    }

    parse->start = p;
    parse->last = (p >= parse->end);

    length = p - start;

    if (nxt_slow_path(length > NXT_CONF_MAX_TOKEN_LEN)) {
        return NXT_ERROR;
    }

    end = nxt_decode_uri(parse->buf, start, length);
    if (nxt_slow_path(end == NULL)) {
        return NXT_ERROR;
    }

    token->length = end - parse->buf;
    token->start = parse->buf;

    return NXT_OK;
}


nxt_conf_value_t *
nxt_conf_get_object_member(nxt_conf_value_t *value, nxt_str_t *name,
    uint32_t *index)
{
    nxt_str_t                 str;
    nxt_uint_t                n;
    nxt_conf_object_t         *object;
    nxt_conf_object_member_t  *member;

    if (value->type != NXT_CONF_VALUE_OBJECT) {
        return NULL;
    }

    object = value->u.object;

    for (n = 0; n < object->count; n++) {
        member = &object->members[n];

        nxt_conf_get_string(&member->name, &str);

        if (nxt_strstr_eq(&str, name)) {

            if (index != NULL) {
                *index = n;
            }

            return &member->value;
        }
    }

    return NULL;
}


nxt_int_t
nxt_conf_map_object(nxt_mp_t *mp, nxt_conf_value_t *value, nxt_conf_map_t *map,
    nxt_uint_t n, void *data)
{
    double            num;
    nxt_str_t         str, *s;
    nxt_uint_t        i;
    nxt_conf_value_t  *v;

    union {
        uint8_t     ui8;
        int32_t     i32;
        int64_t     i64;
        int         i;
        ssize_t     size;
        off_t       off;
        nxt_msec_t  msec;
        double      dbl;
        nxt_str_t   str;
        char        *cstrz;
        void        *v;
    } *ptr;

    for (i = 0; i < n; i++) {

        v = nxt_conf_get_object_member(value, &map[i].name, NULL);

        if (v == NULL || v->type == NXT_CONF_VALUE_NULL) {
            continue;
        }

        ptr = nxt_pointer_to(data, map[i].offset);

        switch (map[i].type) {

        case NXT_CONF_MAP_INT8:

            if (v->type == NXT_CONF_VALUE_BOOLEAN) {
                ptr->ui8 = v->u.boolean;
            }

            break;

        case NXT_CONF_MAP_INT32:
        case NXT_CONF_MAP_INT64:
        case NXT_CONF_MAP_INT:
        case NXT_CONF_MAP_SIZE:
        case NXT_CONF_MAP_OFF:
        case NXT_CONF_MAP_MSEC:

            if (v->type != NXT_CONF_VALUE_INTEGER) {
                break;
            }

            num = nxt_strtod(v->u.number, NULL);

            switch (map[i].type) {

            case NXT_CONF_MAP_INT32:
                ptr->i32 = num;
                break;

            case NXT_CONF_MAP_INT64:
                ptr->i64 = num;
                break;

            case NXT_CONF_MAP_INT:
                ptr->i = num;
                break;

            case NXT_CONF_MAP_SIZE:
                ptr->size = num;
                break;

            case NXT_CONF_MAP_OFF:
                ptr->off = num;
                break;

            case NXT_CONF_MAP_MSEC:
                ptr->msec = (nxt_msec_t) num * 1000;
                break;

            default:
                nxt_unreachable();
            }

            break;

        case NXT_CONF_MAP_DOUBLE:

            if (v->type == NXT_CONF_VALUE_NUMBER) {
                ptr->dbl = nxt_strtod(v->u.number, NULL);
            }

            break;

        case NXT_CONF_MAP_STR:
        case NXT_CONF_MAP_STR_COPY:
        case NXT_CONF_MAP_CSTRZ:

            if (v->type != NXT_CONF_VALUE_SHORT_STRING
                && v->type != NXT_CONF_VALUE_STRING)
            {
                break;
            }

            nxt_conf_get_string(v, &str);

            switch (map[i].type) {

            case NXT_CONF_MAP_STR:
                ptr->str = str;
                break;

            case NXT_CONF_MAP_STR_COPY:

                s = nxt_str_dup(mp, &ptr->str, &str);

                if (nxt_slow_path(s == NULL)) {
                    return NXT_ERROR;
                }

                break;

            case NXT_CONF_MAP_CSTRZ:

                ptr->cstrz = nxt_str_cstrz(mp, &str);

                if (nxt_slow_path(ptr->cstrz == NULL)) {
                    return NXT_ERROR;
                }

                break;

            default:
                nxt_unreachable();
            }

            break;

        case NXT_CONF_MAP_PTR:

            ptr->v = v;

            break;
        }
    }

    return NXT_OK;
}


nxt_conf_value_t *
nxt_conf_next_object_member(nxt_conf_value_t *value, nxt_str_t *name,
    uint32_t *next)
{
    uint32_t                  n;
    nxt_conf_object_t         *object;
    nxt_conf_object_member_t  *member;

    if (value->type != NXT_CONF_VALUE_OBJECT) {
        return NULL;
    }

    n = *next;
    object = value->u.object;

    if (n >= object->count) {
        return NULL;
    }

    member = &object->members[n];
    *next = n + 1;

    nxt_conf_get_string(&member->name, name);

    return &member->value;
}


nxt_conf_value_t *
nxt_conf_get_array_element(nxt_conf_value_t *value, uint32_t index)
{
    nxt_conf_array_t  *array;

    if (value->type != NXT_CONF_VALUE_ARRAY) {
        return NULL;
    }

    array = value->u.array;

    if (index >= array->count) {
        return NULL;
    }

    return &array->elements[index];
}


nxt_conf_value_t *
nxt_conf_get_array_element_or_itself(nxt_conf_value_t *value, uint32_t index)
{
    nxt_conf_array_t  *array;

    if (value->type != NXT_CONF_VALUE_ARRAY) {
        return (index == 0) ? value : NULL;
    }

    array = value->u.array;

    if (index >= array->count) {
        return NULL;
    }

    return &array->elements[index];
}


void
nxt_conf_array_qsort(nxt_conf_value_t *value,
    int (*compare)(const void *, const void *))
{
    nxt_conf_array_t  *array;

    if (value->type != NXT_CONF_VALUE_ARRAY) {
        return;
    }

    array = value->u.array;

    nxt_qsort(array->elements, array->count, sizeof(nxt_conf_value_t), compare);
}


nxt_conf_op_ret_t
nxt_conf_op_compile(nxt_mp_t *mp, nxt_conf_op_t **ops, nxt_conf_value_t *root,
    nxt_str_t *path, nxt_conf_value_t *value, nxt_bool_t add)
{
    nxt_str_t                 token;
    nxt_int_t                 ret, index;
    nxt_conf_op_t             *op, **parent;
    nxt_conf_value_t          *node;
    nxt_conf_path_parse_t     parse;
    nxt_conf_object_member_t  *member;

    parse.start = path->start;
    parse.end = path->start + path->length;
    parse.last = 0;

    parent = ops;

    for ( ;; ) {
        op = nxt_mp_zget(mp, sizeof(nxt_conf_op_t));
        if (nxt_slow_path(op == NULL)) {
            return NXT_CONF_OP_ERROR;
        }

        *parent = op;
        parent = (nxt_conf_op_t **) &op->ctx;

        ret = nxt_conf_path_next_token(&parse, &token);
        if (nxt_slow_path(ret != NXT_OK)) {
            return NXT_CONF_OP_ERROR;
        }

        switch (root->type) {

        case NXT_CONF_VALUE_OBJECT:
            node = nxt_conf_get_object_member(root, &token, &op->index);
            break;

        case NXT_CONF_VALUE_ARRAY:
            index = nxt_int_parse(token.start, token.length);

            if (index < 0 || index > NXT_INT32_T_MAX) {
                return NXT_CONF_OP_NOT_FOUND;
            }

            op->index = index;

            node = nxt_conf_get_array_element(root, index);
            break;

        default:
            node = NULL;
        }

        if (parse.last) {
            break;
        }

        if (node == NULL) {
            return NXT_CONF_OP_NOT_FOUND;
        }

        op->action = NXT_CONF_OP_PASS;
        root = node;
    }

    if (value == NULL) {

        if (node == NULL) {
            return NXT_CONF_OP_NOT_FOUND;
        }

        op->action = NXT_CONF_OP_DELETE;

        return NXT_CONF_OP_OK;
    }

    if (add) {
        if (node == NULL) {
            return NXT_CONF_OP_NOT_FOUND;
        }

        if (node->type != NXT_CONF_VALUE_ARRAY) {
            return NXT_CONF_OP_NOT_ALLOWED;
        }

        op->action = NXT_CONF_OP_PASS;

        op = nxt_mp_zget(mp, sizeof(nxt_conf_op_t));
        if (nxt_slow_path(op == NULL)) {
            return NXT_CONF_OP_ERROR;
        }

        *parent = op;

        op->index = node->u.array->count;
        op->action = NXT_CONF_OP_CREATE;
        op->ctx = value;

        return NXT_CONF_OP_OK;
    }

    if (node != NULL) {
        op->action = NXT_CONF_OP_REPLACE;
        op->ctx = value;

        return NXT_CONF_OP_OK;
    }

    op->action = NXT_CONF_OP_CREATE;

    if (root->type == NXT_CONF_VALUE_ARRAY) {
        if (op->index > root->u.array->count) {
            return NXT_CONF_OP_NOT_FOUND;
        }

        op->ctx = value;

    } else {
        member = nxt_mp_zget(mp, sizeof(nxt_conf_object_member_t));
        if (nxt_slow_path(member == NULL)) {
            return NXT_CONF_OP_ERROR;
        }

        ret = nxt_conf_set_string_dup(&member->name, mp, &token);
        if (nxt_slow_path(ret != NXT_OK)) {
            return NXT_CONF_OP_ERROR;
        }

        member->value = *value;

        op->index = root->u.object->count;
        op->ctx = member;
    }

    return NXT_CONF_OP_OK;
}


nxt_conf_value_t *
nxt_conf_clone(nxt_mp_t *mp, nxt_conf_op_t *op, nxt_conf_value_t *value)
{
    nxt_int_t         rc;
    nxt_conf_value_t  *copy;

    copy = nxt_mp_get(mp, sizeof(nxt_conf_value_t));
    if (nxt_slow_path(copy == NULL)) {
        return NULL;
    }

    rc = nxt_conf_copy_value(mp, op, copy, value);

    if (nxt_slow_path(rc != NXT_OK)) {
        return NULL;
    }

    return copy;
}


static nxt_int_t
nxt_conf_copy_value(nxt_mp_t *mp, nxt_conf_op_t *op, nxt_conf_value_t *dst,
    nxt_conf_value_t *src)
{
    if (op != NULL
        && src->type != NXT_CONF_VALUE_ARRAY
        && src->type != NXT_CONF_VALUE_OBJECT)
    {
        return NXT_ERROR;
    }

    switch (src->type) {

    case NXT_CONF_VALUE_STRING:

        dst->u.string.start = nxt_mp_nget(mp, src->u.string.length);
        if (nxt_slow_path(dst->u.string.start == NULL)) {
            return NXT_ERROR;
        }

        nxt_memcpy(dst->u.string.start, src->u.string.start,
                   src->u.string.length);