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Diffstat (limited to '')
| -rw-r--r-- | lib/json_writer.c | 386 |
1 files changed, 386 insertions, 0 deletions
diff --git a/lib/json_writer.c b/lib/json_writer.c new file mode 100644 index 0000000..2f3936c --- /dev/null +++ b/lib/json_writer.c @@ -0,0 +1,386 @@ +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) */ +/* + * Simple streaming JSON writer + * + * This takes care of the annoying bits of JSON syntax like the commas + * after elements + * + * Authors: Stephen Hemminger <stephen@networkplumber.org> + */ + +#include <stdio.h> +#include <stdbool.h> +#include <stdarg.h> +#include <assert.h> +#include <malloc.h> +#include <inttypes.h> +#include <stdint.h> + +#include "json_writer.h" + +struct json_writer { + FILE *out; /* output file */ + unsigned depth; /* nesting */ + bool pretty; /* optional whitepace */ + char sep; /* either nul or comma */ +}; + +/* indentation for pretty print */ +static void jsonw_indent(json_writer_t *self) +{ + unsigned i; + for (i = 0; i < self->depth; ++i) + fputs(" ", self->out); +} + +/* end current line and indent if pretty printing */ +static void jsonw_eol(json_writer_t *self) +{ + if (!self->pretty) + return; + + putc('\n', self->out); + jsonw_indent(self); +} + +/* If current object is not empty print a comma */ +static void jsonw_eor(json_writer_t *self) +{ + if (self->sep != '\0') + putc(self->sep, self->out); + self->sep = ','; +} + + +/* Output JSON encoded string */ +/* Handles C escapes, does not do Unicode */ +static void jsonw_puts(json_writer_t *self, const char *str) +{ + putc('"', self->out); + for (; *str; ++str) + switch (*str) { + case '\t': + fputs("\\t", self->out); + break; + case '\n': + fputs("\\n", self->out); + break; + case '\r': + fputs("\\r", self->out); + break; + case '\f': + fputs("\\f", self->out); + break; + case '\b': + fputs("\\b", self->out); + break; + case '\\': + fputs("\\\\", self->out); + break; + case '"': + fputs("\\\"", self->out); + break; + default: + putc(*str, self->out); + } + putc('"', self->out); +} + +/* Create a new JSON stream */ +json_writer_t *jsonw_new(FILE *f) +{ + json_writer_t *self = malloc(sizeof(*self)); + if (self) { + self->out = f; + self->depth = 0; + self->pretty = false; + self->sep = '\0'; + } + return self; +} + +/* End output to JSON stream */ +void jsonw_destroy(json_writer_t **self_p) +{ + json_writer_t *self = *self_p; + + assert(self->depth == 0); + fputs("\n", self->out); + fflush(self->out); + free(self); + *self_p = NULL; +} + +void jsonw_pretty(json_writer_t *self, bool on) +{ + self->pretty = on; +} + +/* Basic blocks */ +static void jsonw_begin(json_writer_t *self, int c) +{ + jsonw_eor(self); + putc(c, self->out); + ++self->depth; + self->sep = '\0'; +} + +static void jsonw_end(json_writer_t *self, int c) +{ + assert(self->depth > 0); + + --self->depth; + if (self->sep != '\0') + jsonw_eol(self); + putc(c, self->out); + self->sep = ','; +} + + +/* Add a JSON property name */ +void jsonw_name(json_writer_t *self, const char *name) +{ + jsonw_eor(self); + jsonw_eol(self); + self->sep = '\0'; + jsonw_puts(self, name); + putc(':', self->out); + if (self->pretty) + putc(' ', self->out); +} + +__attribute__((format(printf, 2, 3))) +void jsonw_printf(json_writer_t *self, const char *fmt, ...) +{ + va_list ap; + + va_start(ap, fmt); + jsonw_eor(self); + vfprintf(self->out, fmt, ap); + va_end(ap); +} + +/* Collections */ +void jsonw_start_object(json_writer_t *self) +{ + jsonw_begin(self, '{'); +} + +void jsonw_end_object(json_writer_t *self) +{ + jsonw_end(self, '}'); +} + +void jsonw_start_array(json_writer_t *self) +{ + jsonw_begin(self, '['); + if (self->pretty) + putc(' ', self->out); +} + +void jsonw_end_array(json_writer_t *self) +{ + if (self->pretty && self->sep) + putc(' ', self->out); + self->sep = '\0'; + jsonw_end(self, ']'); +} + +/* JSON value types */ +void jsonw_string(json_writer_t *self, const char *value) +{ + jsonw_eor(self); + jsonw_puts(self, value); +} + +void jsonw_bool(json_writer_t *self, bool val) +{ + jsonw_printf(self, "%s", val ? "true" : "false"); +} + +void jsonw_null(json_writer_t *self) +{ + jsonw_printf(self, "null"); +} + +void jsonw_float(json_writer_t *self, double num) +{ + jsonw_printf(self, "%g", num); +} + +void jsonw_hhu(json_writer_t *self, unsigned char num) +{ + jsonw_printf(self, "%hhu", num); +} + +void jsonw_hu(json_writer_t *self, unsigned short num) +{ + jsonw_printf(self, "%hu", num); +} + +void jsonw_uint(json_writer_t *self, unsigned int num) +{ + jsonw_printf(self, "%u", num); +} + +void jsonw_u64(json_writer_t *self, uint64_t num) +{ + jsonw_printf(self, "%"PRIu64, num); +} + +void jsonw_xint(json_writer_t *self, uint64_t num) +{ + jsonw_printf(self, "%"PRIx64, num); +} + +void jsonw_luint(json_writer_t *self, unsigned long num) +{ + jsonw_printf(self, "%lu", num); +} + +void jsonw_lluint(json_writer_t *self, unsigned long long num) +{ + jsonw_printf(self, "%llu", num); +} + +void jsonw_int(json_writer_t *self, int num) +{ + jsonw_printf(self, "%d", num); +} + +void jsonw_s64(json_writer_t *self, int64_t num) +{ + jsonw_printf(self, "%"PRId64, num); +} + +/* Basic name/value objects */ +void jsonw_string_field(json_writer_t *self, const char *prop, const char *val) +{ + jsonw_name(self, prop); + jsonw_string(self, val); +} + +void jsonw_bool_field(json_writer_t *self, const char *prop, bool val) +{ + jsonw_name(self, prop); + jsonw_bool(self, val); +} + +void jsonw_float_field(json_writer_t *self, const char *prop, double val) +{ + jsonw_name(self, prop); + jsonw_float(self, val); +} + +void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num) +{ + jsonw_name(self, prop); + jsonw_uint(self, num); +} + +void jsonw_u64_field(json_writer_t *self, const char *prop, uint64_t num) +{ + jsonw_name(self, prop); + jsonw_u64(self, num); +} + +void jsonw_xint_field(json_writer_t *self, const char *prop, uint64_t num) +{ + jsonw_name(self, prop); + jsonw_xint(self, num); +} + +void jsonw_hhu_field(json_writer_t *self, const char *prop, unsigned char num) +{ + jsonw_name(self, prop); + jsonw_hhu(self, num); +} + +void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num) +{ + jsonw_name(self, prop); + jsonw_hu(self, num); +} + +void jsonw_luint_field(json_writer_t *self, + const char *prop, + unsigned long num) +{ + jsonw_name(self, prop); + jsonw_luint(self, num); +} + +void jsonw_lluint_field(json_writer_t *self, + const char *prop, + unsigned long long num) +{ + jsonw_name(self, prop); + jsonw_lluint(self, num); +} + +void jsonw_int_field(json_writer_t *self, const char *prop, int num) +{ + jsonw_name(self, prop); + jsonw_int(self, num); +} + +void jsonw_s64_field(json_writer_t *self, const char *prop, int64_t num) +{ + jsonw_name(self, prop); + jsonw_s64(self, num); +} + +void jsonw_null_field(json_writer_t *self, const char *prop) +{ + jsonw_name(self, prop); + jsonw_null(self); +} + +#ifdef TEST +int main(int argc, char **argv) +{ + json_writer_t *wr = jsonw_new(stdout); + + jsonw_start_object(wr); + jsonw_pretty(wr, true); + jsonw_name(wr, "Vyatta"); + jsonw_start_object(wr); + jsonw_string_field(wr, "url", "http://vyatta.com"); + jsonw_uint_field(wr, "downloads", 2000000ul); + jsonw_float_field(wr, "stock", 8.16); + + jsonw_name(wr, "ARGV"); + jsonw_start_array(wr); + while (--argc) + jsonw_string(wr, *++argv); + jsonw_end_array(wr); + + jsonw_name(wr, "empty"); + jsonw_start_array(wr); + jsonw_end_array(wr); + + jsonw_name(wr, "NIL"); + jsonw_start_object(wr); + jsonw_end_object(wr); + + jsonw_null_field(wr, "my_null"); + + jsonw_name(wr, "special chars"); + jsonw_start_array(wr); + jsonw_string_field(wr, "slash", "/"); + jsonw_string_field(wr, "newline", "\n"); + jsonw_string_field(wr, "tab", "\t"); + jsonw_string_field(wr, "ff", "\f"); + jsonw_string_field(wr, "quote", "\""); + jsonw_string_field(wr, "tick", "\'"); + jsonw_string_field(wr, "backslash", "\\"); + jsonw_end_array(wr); + + jsonw_end_object(wr); + + jsonw_end_object(wr); + jsonw_destroy(&wr); + return 0; +} + +#endif |