1 files changed, 355 insertions, 0 deletions
diff --git a/src/contrib/wire_ctx.h b/src/contrib/wire_ctx.h
new file mode 100644
index 0000000..f4f1789
--- /dev/null
+++ b/src/contrib/wire_ctx.h
@@ -0,0 +1,355 @@
+/*  Copyright (C) 2019 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "contrib/string.h"
+#include "libknot/endian.h"
+#include "libknot/errcode.h"
+
+/*!
+ * \brief Struct to keep the wire context.
+ */
+typedef struct wire_ctx {
+	size_t size;
+	uint8_t *wire;
+	uint8_t *position;
+	int error;
+	bool readonly;
+} wire_ctx_t;
+
+/*!
+ * \brief Initialize wire context.
+ */
+static inline wire_ctx_t wire_ctx_init(uint8_t *data, size_t size)
+{
+	assert(data);
+
+	wire_ctx_t result = {
+		.size = size,
+		.wire = data,
+		.position = data,
+		.error = KNOT_EOK,
+		.readonly = false
+	};
+
+	return result;
+}
+
+/*!
+ * \brief Initialize read only wire context.
+ *
+ * \note No write is performed, and error is set to KNOT_EACCES.
+ *
+ */
+static inline wire_ctx_t wire_ctx_init_const(const uint8_t *data, size_t size)
+{
+	assert(data);
+
+	wire_ctx_t result = wire_ctx_init((uint8_t *)data, size);
+	result.readonly = true;
+
+	return result;
+}
+
+/*!
+ * \brief Gets actual position.
+ *
+ * \return position from the begin.
+ */
+static inline size_t wire_ctx_offset(wire_ctx_t *ctx)
+{
+	assert(ctx);
+
+	return ctx->position - ctx->wire;
+}
+
+/*!
+ * \brief Set position offset from the begin.
+ *
+ * \param offset Wire offset (starts from 0).
+ *
+ * \note Noop if previous error.
+ */
+static inline void wire_ctx_set_offset(wire_ctx_t *ctx, size_t offset)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	if (offset > ctx->size) {
+		ctx->error = KNOT_ERANGE;
+		return;
+	}
+
+	ctx->position = ctx->wire + offset;
+}
+
+/*!
+ * \brief Gets available bytes.
+ *
+ * \return Number of bytes to end.
+ */
+static inline size_t wire_ctx_available(wire_ctx_t *ctx)
+{
+	assert(ctx);
+
+	return ctx->size - wire_ctx_offset(ctx);
+}
+
+/*!
+ * \brief Add offset to the current position.
+ *
+ * \note Noop if previous error.
+ */
+static inline void wire_ctx_skip(wire_ctx_t *ctx, ssize_t offset)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	// Check for out of scope skip.
+	if (offset >= 0) {
+		if (offset > wire_ctx_available(ctx)) {
+			ctx->error = KNOT_ERANGE;
+			return;
+		}
+	} else {
+		if (-offset > wire_ctx_offset(ctx)) {
+			ctx->error = KNOT_ERANGE;
+			return;
+		}
+	}
+
+	ctx->position += offset;
+}
+
+/*!
+ * \brief Check the context if reading is possible.
+ */
+static inline int wire_ctx_can_read(wire_ctx_t *ctx, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return ctx->error;
+	}
+
+	if (wire_ctx_available(ctx) < size) {
+		return KNOT_EFEWDATA;
+	}
+
+	return KNOT_EOK;
+}
+
+/*!
+ * \brief Check the context if writing is possible.
+ */
+static inline int wire_ctx_can_write(wire_ctx_t *ctx, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return ctx->error;
+	}
+
+	if (ctx->readonly) {
+		return KNOT_EACCES;
+	}
+
+	if (wire_ctx_available(ctx) < size) {
+		return KNOT_ESPACE;
+	}
+
+	return KNOT_EOK;
+}
+
+
+static inline void wire_ctx_read(wire_ctx_t *ctx, void *data, size_t size)
+{
+	assert(ctx);
+	assert(data);
+
+	if (ctx->error != KNOT_EOK) {
+		/* Avoid leaving data uninitialized. */
+		memzero(data, size);
+		return;
+	}
+
+	int ret = wire_ctx_can_read(ctx, size);
+	if (ret != KNOT_EOK) {
+		ctx->error = ret;
+		memzero(data, size);
+		return;
+	}
+
+	memcpy(data, ctx->position, size);
+	ctx->position += size;
+}
+
+static inline uint8_t wire_ctx_read_u8(wire_ctx_t *ctx)
+{
+	uint8_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return result;
+}
+
+static inline uint16_t wire_ctx_read_u16(wire_ctx_t *ctx)
+{
+	uint16_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return be16toh(result);
+}
+
+static inline uint32_t wire_ctx_read_u32(wire_ctx_t *ctx)
+{
+	uint32_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return be32toh(result);
+}
+
+static inline uint64_t wire_ctx_read_u48(wire_ctx_t *ctx)
+{
+	/* This case is slightly tricky. */
+	uint64_t result = 0;
+	wire_ctx_read(ctx, (uint8_t *)&result + 1, 6);
+
+	return be64toh(result) >> 8;
+}
+
+static inline uint64_t wire_ctx_read_u64(wire_ctx_t *ctx)
+{
+	uint64_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return be64toh(result);
+}
+
+
+static inline void wire_ctx_write(wire_ctx_t *ctx, const void *data, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	if (size == 0) {
+		return;
+	}
+
+	assert(data);
+
+	int ret = wire_ctx_can_write(ctx, size);
+	if (ret != KNOT_EOK) {
+		ctx->error = ret;
+		return;
+	}
+
+	memcpy(ctx->position, data, size);
+	ctx->position += size;
+}
+
+static inline void wire_ctx_write_u8(wire_ctx_t *ctx, uint8_t value)
+{
+	wire_ctx_write(ctx, &value, sizeof(value));
+}
+
+static inline void wire_ctx_write_u16(wire_ctx_t *ctx, uint16_t value)
+{
+	uint16_t beval = htobe16(value);
+	wire_ctx_write(ctx, &beval, sizeof(beval));
+}
+
+static inline void wire_ctx_write_u32(wire_ctx_t *ctx, uint32_t value)
+{
+	uint32_t beval = htobe32(value);
+	wire_ctx_write(ctx, &beval, sizeof(beval));
+}
+
+static inline void wire_ctx_write_u48(wire_ctx_t *ctx, uint64_t value)
+{
+	/* This case is slightly tricky. */
+	uint64_t swapped = htobe64(value << 8);
+	wire_ctx_write(ctx, (uint8_t *)&swapped + 1, 6);
+}
+
+static inline void wire_ctx_write_u64(wire_ctx_t *ctx, uint64_t value)
+{
+	uint64_t beval = htobe64(value);
+	wire_ctx_write(ctx, &beval, sizeof(beval));
+}
+
+static inline void wire_ctx_clear(wire_ctx_t *ctx, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	if (size == 0) {
+		return;
+	}
+
+	int ret = wire_ctx_can_write(ctx, size);
+	if (ret != KNOT_EOK) {
+		ctx->error = ret;
+		return;
+	}
+
+	memzero(ctx->position, size);
+	ctx->position += size;
+}
+
+static inline void wire_ctx_copy(wire_ctx_t *dst, wire_ctx_t *src, size_t size)
+{
+	assert(dst);
+	assert(src);
+
+	if (size == 0 || dst->error != KNOT_EOK) {
+		return;
+	}
+
+	if (wire_ctx_can_read(src, size) != KNOT_EOK) {
+		dst->error = KNOT_EFEWDATA;
+		return;
+	}
+
+	int ret = wire_ctx_can_write(dst, size);
+	if (ret != KNOT_EOK) {
+		dst->error = ret;
+		return;
+	}
+
+	memcpy(dst->position, src->position, size);
+	dst->position += size;
+	src->position += size;
+}