src/cn-encoder.c

#ifndef CN_ENCODER_C
#define CN_ENCODER_C

#ifdef __cplusplus
extern "C" {
#endif
#ifdef EMACS_INDENTATION_HELPER
} /* Duh. */
#endif

#ifdef _MSC_VER
#include <WinSock2.h>
#define inline _inline
#else
#ifndef __MBED__
#include <arpa/inet.h>
#endif
#endif
#include <string.h>
#ifndef _MSC_VER
#ifndef __MBED__
#include <strings.h>
#endif
#endif
#include <stdbool.h>
#include <assert.h>

#include "dll-export.h"
#include "cn-cbor/cn-cbor.h"
#include "cbor.h"

#define hton8p(p) (*(uint8_t *)(p))
#define hton16p(p) (htons(*(uint16_t *)(p)))
#define hton32p(p) (htonl(*(uint32_t *)(p)))
static uint64_t hton64p(const uint8_t *p)
{
	/* TODO: does this work on both BE and LE systems? */
	uint64_t ret = hton32p(p);
	ret <<= 32;
	ret |= hton32p(p + 4);
	return ret;
}

typedef struct _write_state {
	uint8_t *buf;
	size_t offset;
	size_t size;
} cn_write_state;

#define ensure_writable(sz)                                                          \
	if ((ws->buf != NULL) && (ws->offset + (sz) > ws->size)) { \
		return false;                                                                \
	}

#define write_byte_and_data(b, data, sz)            \
	if (ws->buf) {                                  \
		ws->buf[ws->offset++] = (b);                \
		memcpy(ws->buf + ws->offset, (data), (sz)); \
	}                                               \
	else {                                          \
		ws->offset++;                               \
	}                                               \
	ws->offset += sz;

#define write_byte(b)                \
	if (ws->buf) {                   \
		ws->buf[ws->offset++] = (b); \
	}                                \
	else {                           \
		ws->offset++;                \
	}

#define write_byte_ensured(b) \
	ensure_writable(1);       \
	write_byte(b);

static const uint8_t _xlate[] = {
	IB_FALSE,	 /* CN_CBOR_FALSE */
	IB_TRUE,	 /* CN_CBOR_TRUE */
	IB_NIL,		 /* CN_CBOR_NULL */
	IB_UNDEF,	 /* CN_CBOR_UNDEF */
	IB_UNSIGNED, /* CN_CBOR_UINT */
	IB_NEGATIVE, /* CN_CBOR_INT */
	IB_BYTES,	 /* CN_CBOR_BYTES */
	IB_TEXT,	 /* CN_CBOR_TEXT */
	IB_BYTES,	 /* CN_CBOR_BYTES_CHUNKED */
	IB_TEXT,	 /* CN_CBOR_TEXT_CHUNKED */
	IB_ARRAY,	 /* CN_CBOR_ARRAY */
	IB_MAP,		 /* CN_CBOR_MAP */
	IB_TAG,		 /* CN_CBOR_TAG */
	IB_PRIM,	 /* CN_CBOR_SIMPLE */
	0xFF,		 /* CN_CBOR_DOUBLE */
	0xFF		 /* CN_CBOR_INVALID */
};

static inline bool is_indefinite(const cn_cbor *cb)
{
	return (cb->flags & CN_CBOR_FL_INDEF) != 0;
}

static bool _write_positive(cn_write_state *ws, cn_cbor_type typ, uint64_t val)
{
	assert((size_t)typ < sizeof(_xlate));
	if (typ >= (int) sizeof(_xlate)) {
		return false;
	}

	const uint8_t ib = _xlate[typ];
	if (ib == 0xFF) {
		return false;
	}

	if (val < 24) {
		ensure_writable(1);
		write_byte(ib | (uint8_t)val);
	}
	else if (val < 256) {
		ensure_writable(2);
		write_byte(ib | 24);
		write_byte((uint8_t)val);
	}
	else if (val < 65536) {
		uint16_t be16 = (uint16_t)val;
		ensure_writable(3);
		be16 = hton16p(&be16);
		write_byte_and_data(ib | 25, (const void *)&be16, 2);
	}
	else if (val < 0x100000000L) {
		uint32_t be32 = (uint32_t)val;
		ensure_writable(5);
		// be32 = hton32p(&be32);
		be32 = htonl(be32);
		write_byte_and_data(ib | 26, (const void *)&be32, 4);
	}
	else {
		uint64_t be64;
		ensure_writable(9);
		be64 = hton64p((const uint8_t *)&val);
		write_byte_and_data(ib | 27, (const void *)&be64, 8);
	}

	return true;
}

#ifndef CBOR_NO_FLOAT
static bool _write_double(cn_write_state *ws, double val, int size)
{
	float float_val = (float)val;
	if (float_val == val && (size != 64)) { /* 32 bits is enough and we aren't NaN */
		uint32_t be32;
		uint16_t be16, u16;
		union {
			float f;
			uint32_t u;
		} u32;
		u32.f = float_val;

		if ((u32.u & 0x1FFF) == 0 && (size == 0)) { /* worth trying half */
			int s16 = (u32.u >> 16) & 0x8000;
			int exp = (int)((u32.u >> 23) & 0xff);
			int mant = (int)(u32.u & 0x7fffff);
			if (exp == 0 && mant == 0) {
				; /* 0.0, -0.0 */
			}
			else if (exp >= 113 && exp <= 142) {
				/* normalized */
				s16 += ((exp - 112) << 10) + (mant >> 13);
			}
			else if (exp >= 103 && exp < 113) { /* denorm, exp16 = 0 */
				if (mant & ((1 << (126 - exp)) - 1)) {
					goto float32; /* loss of precision */
				}
				s16 += ((mant + 0x800000) >> (126 - exp));
			}
			else if (exp == 255 && mant == 0) { /* Inf */
				s16 += 0x7c00;
			}
			else {
				goto float32; /* loss of range */
			}

			ensure_writable(3);
			u16 = s16;
			be16 = hton16p((const uint8_t *)&u16);

			write_byte_and_data(IB_PRIM | 25, (const void *)&be16, 2);
			return true;
		}
	float32:
		ensure_writable(5);
		be32 = hton32p((const uint8_t *)&u32.u);

		write_byte_and_data(IB_PRIM | 26, (const void *)&be32, 4);
	}
	else if (val != val) { /* NaN -- we always write a half NaN*/
		ensure_writable(3);
		write_byte_and_data(IB_PRIM | 25, (const void *)"\x7e\x00", 2);
	}
	else {
		uint64_t be64;
		/* Copy the same problematic implementation from the decoder. */
		union {
			double d;
			uint64_t u;
		} u64;

		u64.d = val;

		ensure_writable(9);
		be64 = hton64p((const uint8_t *)&u64.u);

		write_byte_and_data(IB_PRIM | 27, (const void *)&be64, 8);
	}
	return true;
}
#endif /* CBOR_NO_FLOAT */

// TODO: make public?
typedef bool (*cn_visit_func)(const cn_cbor *cb, int depth, void *context);
bool _visit(const cn_cbor *cb, cn_visit_func visitor, cn_visit_func breaker, void *context)
{
	const cn_cbor *p = cb;
	int depth = 0;
	while (p) {
	visit:
		if (!visitor(p, depth, context)) {
			return false;
		}

		if (p->first_child) {
			p = p->first_child;
			depth++;
		}
		else {
			// Empty indefinite
#ifdef CN_INCLUDE_DUMPER
			if (!breaker(p, depth, context)) {
				return false;
			}
#else
			if (is_indefinite(p)) {
				if (!breaker(p, depth, context)) {
					return false;
				}
			}
#endif
			if (p->next) {
				p = p->next;
			}
			else {
				while (p->parent) {
					depth--;
#ifdef CN_INCLUDE_DUMPER
					if (!breaker(p->parent, depth, context)) {
						return false;
					}
#else
					if (is_indefinite(p->parent)) {
						if (!breaker(p->parent, depth, context)) {
							return false;
						}
					}
#endif
					if (p->parent->next) {
						p = p->parent->next;
						goto visit;
					}
					p = p->parent;
				}
				return true;
			}
		}
	}
	return true;
}

#define CHECK(st)     \
	if (!(st)) {      \
		return false; \
	}

bool _encoder_visitor(const cn_cbor *cb, int depth, void *context)
{
	cn_write_state *ws = context;
	UNUSED_PARAM(depth);

	switch (cb->type) {
		case CN_CBOR_ARRAY:
			if (is_indefinite(cb)) {
				write_byte_ensured(IB_ARRAY | AI_INDEF);
			}
			else {
				CHECK(_write_positive(ws, CN_CBOR_ARRAY, cb->length));
			}
			break;

		case CN_CBOR_MAP:
			if (is_indefinite(cb)) {
				write_byte_ensured(IB_MAP | AI_INDEF);
			}
			else {
				CHECK(_write_positive(ws, CN_CBOR_MAP, cb->length / 2));
			}
			break;

		case CN_CBOR_BYTES_CHUNKED:
		case CN_CBOR_TEXT_CHUNKED:
			write_byte_ensured(_xlate[cb->type] | AI_INDEF);
			break;

		case CN_CBOR_TEXT:
		case CN_CBOR_BYTES:
			CHECK(_write_positive(ws, cb->type, cb->length));
			ensure_writable(cb->length);
			if (ws->buf) {
				memcpy(ws->buf + ws->offset, cb->v.str, cb->length);
			}
			ws->offset += cb->length;
			break;

		case CN_CBOR_FALSE:
		case CN_CBOR_TRUE:
		case CN_CBOR_NULL:
		case CN_CBOR_UNDEF:
			write_byte_ensured(_xlate[cb->type]);
			break;

		case CN_CBOR_TAG:
		case CN_CBOR_UINT:
		case CN_CBOR_SIMPLE:
			CHECK(_write_positive(ws, cb->type, cb->v.uint));
			break;

		case CN_CBOR_INT:
			assert(cb->v.sint < 0);
			CHECK(_write_positive(ws, CN_CBOR_INT, ~(cb->v.sint)));
			break;

#ifndef CBOR_NO_FLOAT
		case CN_CBOR_DOUBLE:
			CHECK(_write_double(ws, cb->v.dbl, (cb->flags & CN_CBOR_FL_KEEP_FLOAT_SIZE) ? 64 : 0));
			break;

		case CN_CBOR_FLOAT:
			CHECK(_write_double(ws, cb->v.f, (cb->flags & CN_CBOR_FL_KEEP_FLOAT_SIZE) ? 32 : 0));
			break;
#endif /* CBOR_NO_FLOAT */

		case CN_CBOR_INVALID:
		default:
			return false;
	}

	return true;
}

bool _encoder_breaker(const cn_cbor *cb, int depth, void *context)
{
	cn_write_state *ws = context;
	UNUSED_PARAM(cb);
	UNUSED_PARAM(depth);
#ifdef CN_INCLUDE_DUMPER
	if (is_indefinite(cb)) {
#endif
		write_byte_ensured(IB_BREAK);
#ifdef CN_INCLUDE_DUMPER
	}
#endif
	return true;
}

ssize_t cn_cbor_encoder_write(uint8_t *buf, size_t buf_offset, size_t buf_size, const cn_cbor *cb)
{
	cn_write_state ws = {buf, buf_offset, buf_size - buf_offset};
	if (!ws.buf && ws.size <= 0) {
		ws.size = (ssize_t)(((size_t)-1) / 2);
	}
	if (!_visit(cb, _encoder_visitor, _encoder_breaker, &ws)) {
		return -1;
	}
	return (ssize_t)(ws.offset - buf_offset);
}

#ifdef __cplusplus
}
#endif

#endif /* CN_CBOR_C */