json: Implement wrapping interface
While the newly added jsmn library provides the parsing interface, it does not provide any kind of interface to act on parsed tokens. Instead, the caller is expected to handle pointer arithmetics inside of the token array in order to extract required information. While simple, this requires users to know some of the inner workings of the library and is thus quite an unintuitive interface. This commit adds a new interface on top of the jsmn parser that provides convenience functions to retrieve values from the parsed json type, grub_json_t. Signed-off-by: Patrick Steinhardt <ps@pks.im> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Patrick Steinhardt
Daniel Kiper
parent
528938d503
commit
c6a84545a3
2 changed files with 366 additions and 0 deletions
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@ -17,7 +17,251 @@
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*/
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#include <grub/dl.h>
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#include <grub/mm.h>
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#define JSMN_STATIC
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#include "jsmn.h"
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#include "json.h"
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GRUB_MOD_LICENSE ("GPLv3");
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grub_err_t
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grub_json_parse (grub_json_t **out, char *string, grub_size_t string_len)
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{
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grub_json_t *json = NULL;
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jsmn_parser parser;
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grub_err_t ret = GRUB_ERR_NONE;
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int jsmn_ret;
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if (!string)
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return GRUB_ERR_BAD_ARGUMENT;
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json = grub_zalloc (sizeof (*json));
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if (!json)
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return GRUB_ERR_OUT_OF_MEMORY;
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json->string = string;
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/*
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* Parse the string twice: first to determine how many tokens
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* we need to allocate, second to fill allocated tokens.
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*/
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jsmn_init (&parser);
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jsmn_ret = jsmn_parse (&parser, string, string_len, NULL, 0);
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if (jsmn_ret <= 0)
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{
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ret = GRUB_ERR_BAD_ARGUMENT;
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goto err;
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}
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json->tokens = grub_malloc (sizeof (jsmntok_t) * jsmn_ret);
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if (!json->tokens)
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{
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ret = GRUB_ERR_OUT_OF_MEMORY;
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goto err;
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}
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jsmn_init (&parser);
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jsmn_ret = jsmn_parse (&parser, string, string_len, json->tokens, jsmn_ret);
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if (jsmn_ret <= 0)
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{
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ret = GRUB_ERR_BAD_ARGUMENT;
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goto err;
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}
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*out = json;
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err:
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if (ret && json)
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{
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grub_free (json->string);
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grub_free (json->tokens);
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grub_free (json);
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}
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return ret;
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}
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void
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grub_json_free (grub_json_t *json)
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{
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if (json)
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{
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grub_free (json->tokens);
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grub_free (json);
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}
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}
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grub_err_t
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grub_json_getsize (grub_size_t *out, const grub_json_t *json)
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{
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int size;
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size = ((jsmntok_t *)json->tokens)[json->idx].size;
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if (size < 0)
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return GRUB_ERR_OUT_OF_RANGE;
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*out = (grub_size_t) size;
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return GRUB_ERR_NONE;
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}
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grub_err_t
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grub_json_gettype (grub_json_type_t *out, const grub_json_t *json)
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{
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switch (((jsmntok_t *)json->tokens)[json->idx].type)
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{
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case JSMN_OBJECT:
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*out = GRUB_JSON_OBJECT;
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break;
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case JSMN_ARRAY:
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*out = GRUB_JSON_ARRAY;
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break;
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case JSMN_STRING:
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*out = GRUB_JSON_STRING;
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break;
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case JSMN_PRIMITIVE:
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*out = GRUB_JSON_PRIMITIVE;
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break;
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default:
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return GRUB_ERR_BAD_ARGUMENT;
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}
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return GRUB_ERR_NONE;
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}
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grub_err_t
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grub_json_getchild (grub_json_t *out, const grub_json_t *parent, grub_size_t n)
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{
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grub_size_t offset = 1, size;
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jsmntok_t *p;
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if (grub_json_getsize (&size, parent) || n >= size)
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return GRUB_ERR_OUT_OF_RANGE;
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/*
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* Skip the first n children. For each of the children, we need
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* to skip their own potential children (e.g. if it's an
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* array), as well. We thus add the children's size to n on
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* each iteration.
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*/
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p = &((jsmntok_t *)parent->tokens)[parent->idx];
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while (n--)
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n += p[offset++].size;
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out->string = parent->string;
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out->tokens = parent->tokens;
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out->idx = parent->idx + offset;
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return GRUB_ERR_NONE;
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}
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grub_err_t
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grub_json_getvalue (grub_json_t *out, const grub_json_t *parent, const char *key)
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{
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grub_json_type_t type;
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grub_size_t i, size;
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if (grub_json_gettype (&type, parent) || type != GRUB_JSON_OBJECT)
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return GRUB_ERR_BAD_ARGUMENT;
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if (grub_json_getsize (&size, parent))
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return GRUB_ERR_BAD_ARGUMENT;
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for (i = 0; i < size; i++)
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{
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grub_json_t child;
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const char *s;
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if (grub_json_getchild (&child, parent, i) ||
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grub_json_getstring (&s, &child, NULL) ||
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grub_strcmp (s, key) != 0)
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continue;
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return grub_json_getchild (out, &child, 0);
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}
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return GRUB_ERR_FILE_NOT_FOUND;
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}
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static grub_err_t
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get_value (grub_json_type_t *out_type, const char **out_string, const grub_json_t *parent, const char *key)
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{
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const grub_json_t *p = parent;
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grub_json_t child;
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grub_err_t ret;
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jsmntok_t *tok;
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if (key)
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{
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ret = grub_json_getvalue (&child, parent, key);
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if (ret)
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return ret;
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p = &child;
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}
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tok = &((jsmntok_t *) p->tokens)[p->idx];
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p->string[tok->end] = '\0';
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*out_string = p->string + tok->start;
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return grub_json_gettype (out_type, p);
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}
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grub_err_t
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grub_json_getstring (const char **out, const grub_json_t *parent, const char *key)
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{
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grub_json_type_t type;
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const char *value;
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grub_err_t ret;
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ret = get_value (&type, &value, parent, key);
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if (ret)
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return ret;
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if (type != GRUB_JSON_STRING)
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return GRUB_ERR_BAD_ARGUMENT;
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*out = value;
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return GRUB_ERR_NONE;
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}
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grub_err_t
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grub_json_getuint64 (grub_uint64_t *out, const grub_json_t *parent, const char *key)
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{
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grub_json_type_t type;
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const char *value;
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char *end;
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grub_err_t ret;
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ret = get_value (&type, &value, parent, key);
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if (ret)
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return ret;
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if (type != GRUB_JSON_STRING && type != GRUB_JSON_PRIMITIVE)
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return GRUB_ERR_BAD_ARGUMENT;
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grub_errno = GRUB_ERR_NONE;
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*out = grub_strtoul (value, &end, 10);
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if (grub_errno != GRUB_ERR_NONE || *end)
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return GRUB_ERR_BAD_NUMBER;
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return GRUB_ERR_NONE;
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}
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grub_err_t
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grub_json_getint64 (grub_int64_t *out, const grub_json_t *parent, const char *key)
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{
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grub_json_type_t type;
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const char *value;
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char *end;
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grub_err_t ret;
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ret = get_value (&type, &value, parent, key);
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if (ret)
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return ret;
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if (type != GRUB_JSON_STRING && type != GRUB_JSON_PRIMITIVE)
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return GRUB_ERR_BAD_ARGUMENT;
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grub_errno = GRUB_ERR_NONE;
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*out = grub_strtol (value, &end, 10);
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if (grub_errno != GRUB_ERR_NONE || *end)
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return GRUB_ERR_BAD_NUMBER;
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return GRUB_ERR_NONE;
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}
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