← Back
Editing: lwbuffer.h
/* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, you can obtain one at https://mozilla.org/MPL/2.0/. * * See the COPYRIGHT file distributed with this work for additional * information regarding copyright ownership. */ /*! \file lwres/lwbuffer.h * * A buffer is a region of memory, together with a set of related subregions. * Buffers are used for parsing and I/O operations. * * The 'used region' and the 'available' region are disjoint, and their * union is the buffer's region. The used region extends from the beginning * of the buffer region to the last used byte. The available region * extends from one byte greater than the last used byte to the end of the * buffer's region. The size of the used region can be changed using various * buffer commands. Initially, the used region is empty. * * The used region is further subdivided into two disjoint regions: the * 'consumed region' and the 'remaining region'. The union of these two * regions is the used region. The consumed region extends from the beginning * of the used region to the byte before the 'current' offset (if any). The * 'remaining' region the current pointer to the end of the used * region. The size of the consumed region can be changed using various * buffer commands. Initially, the consumed region is empty. * * The 'active region' is an (optional) subregion of the remaining region. * It extends from the current offset to an offset in the remaining region * that is selected with lwres_buffer_setactive(). Initially, the active * region is empty. If the current offset advances beyond the chosen offset, * the active region will also be empty. * * \verbatim * /----- used region -----\/-- available --\ * +----------------------------------------+ * | consumed | remaining | | * +----------------------------------------+ * a b c d e * * a == base of buffer. * b == current pointer. Can be anywhere between a and d. * c == active pointer. Meaningful between b and d. * d == used pointer. * e == length of buffer. * * a-e == entire (length) of buffer. * a-d == used region. * a-b == consumed region. * b-d == remaining region. * b-c == optional active region. * \endverbatim * * The following invariants are maintained by all routines: * *\verbatim * length > 0 * * base is a valid pointer to length bytes of memory * * 0 <= used <= length * * 0 <= current <= used * * 0 <= active <= used * (although active < current implies empty active region) *\endverbatim * * \li MP: * Buffers have no synchronization. Clients must ensure exclusive * access. * * \li Reliability: * No anticipated impact. * * \li Resources: * Memory: 1 pointer + 6 unsigned integers per buffer. * * \li Security: * No anticipated impact. * * \li Standards: * None. */ #ifndef LWRES_LWBUFFER_H #define LWRES_LWBUFFER_H 1 /*** *** Imports ***/ #include <inttypes.h> #include <lwres/lang.h> LWRES_LANG_BEGINDECLS /*** *** Magic numbers ***/ #define LWRES_BUFFER_MAGIC 0x4275663fU /* Buf?. */ #define LWRES_BUFFER_VALID(b) ((b) != NULL && \ (b)->magic == LWRES_BUFFER_MAGIC) /*! * The following macros MUST be used only on valid buffers. It is the * caller's responsibility to ensure this by using the LWRES_BUFFER_VALID * check above, or by calling another lwres_buffer_*() function (rather than * another macro.) */ /*! * Get the length of the used region of buffer "b" */ #define LWRES_BUFFER_USEDCOUNT(b) ((b)->used) /*! * Get the length of the available region of buffer "b" */ #define LWRES_BUFFER_AVAILABLECOUNT(b) ((b)->length - (b)->used) #define LWRES_BUFFER_REMAINING(b) ((b)->used - (b)->current) /*! * Note that the buffer structure is public. This is principally so buffer * operations can be implemented using macros. Applications are strongly * discouraged from directly manipulating the structure. */ typedef struct lwres_buffer lwres_buffer_t; /*! * Buffer data structure */ struct lwres_buffer { unsigned int magic; unsigned char *base; /* The following integers are byte offsets from 'base'. */ unsigned int length; unsigned int used; unsigned int current; unsigned int active; }; /*** *** Functions ***/ void lwres_buffer_init(lwres_buffer_t *b, void *base, unsigned int length); /**< * Make 'b' refer to the 'length'-byte region starting at base. * * Requires: * * 'length' > 0 * * 'base' is a pointer to a sequence of 'length' bytes. * */ void lwres_buffer_invalidate(lwres_buffer_t *b); /**< * Make 'b' an invalid buffer. * * Requires: * 'b' is a valid buffer. * * Ensures: * If assertion checking is enabled, future attempts to use 'b' without * calling lwres_buffer_init() on it will cause an assertion failure. */ void lwres_buffer_add(lwres_buffer_t *b, unsigned int n); /**< * Increase the 'used' region of 'b' by 'n' bytes. * * Requires: * * 'b' is a valid buffer * * used + n <= length * */ void lwres_buffer_subtract(lwres_buffer_t *b, unsigned int n); /**< * Decrease the 'used' region of 'b' by 'n' bytes. * * Requires: * * 'b' is a valid buffer * * used >= n * */ void lwres_buffer_clear(lwres_buffer_t *b); /**< * Make the used region empty. * * Requires: * * 'b' is a valid buffer * * Ensures: * * used = 0 * */ void lwres_buffer_first(lwres_buffer_t *b); /**< * Make the consumed region empty. * * Requires: * * 'b' is a valid buffer * * Ensures: * * current == 0 * */ void lwres_buffer_forward(lwres_buffer_t *b, unsigned int n); /**< * Increase the 'consumed' region of 'b' by 'n' bytes. * * Requires: * * 'b' is a valid buffer * * current + n <= used * */ void lwres_buffer_back(lwres_buffer_t *b, unsigned int n); /**< * Decrease the 'consumed' region of 'b' by 'n' bytes. * * Requires: * * 'b' is a valid buffer * * n <= current * */ uint8_t lwres_buffer_getuint8(lwres_buffer_t *b); /**< * Read an unsigned 8-bit integer from 'b' and return it. * * Requires: * * 'b' is a valid buffer. * * The length of the available region of 'b' is at least 1. * * Ensures: * * The current pointer in 'b' is advanced by 1. * * Returns: * * A 8-bit unsigned integer. */ void lwres_buffer_putuint8(lwres_buffer_t *b, uint8_t val); /**< * Store an unsigned 8-bit integer from 'val' into 'b'. * * Requires: * 'b' is a valid buffer. * * The length of the unused region of 'b' is at least 1. * * Ensures: * The used pointer in 'b' is advanced by 1. */ uint16_t lwres_buffer_getuint16(lwres_buffer_t *b); /**< * Read an unsigned 16-bit integer in network byte order from 'b', convert * it to host byte order, and return it. * * Requires: * * 'b' is a valid buffer. * * The length of the available region of 'b' is at least 2. * * Ensures: * * The current pointer in 'b' is advanced by 2. * * Returns: * * A 16-bit unsigned integer. */ void lwres_buffer_putuint16(lwres_buffer_t *b, uint16_t val); /**< * Store an unsigned 16-bit integer in host byte order from 'val' * into 'b' in network byte order. * * Requires: * 'b' is a valid buffer. * * The length of the unused region of 'b' is at least 2. * * Ensures: * The used pointer in 'b' is advanced by 2. */ uint32_t lwres_buffer_getuint32(lwres_buffer_t *b); /**< * Read an unsigned 32-bit integer in network byte order from 'b', convert * it to host byte order, and return it. * * Requires: * * 'b' is a valid buffer. * * The length of the available region of 'b' is at least 2. * * Ensures: * * The current pointer in 'b' is advanced by 2. * * Returns: * * A 32-bit unsigned integer. */ void lwres_buffer_putuint32(lwres_buffer_t *b, uint32_t val); /**< * Store an unsigned 32-bit integer in host byte order from 'val' * into 'b' in network byte order. * * Requires: * 'b' is a valid buffer. * * The length of the unused region of 'b' is at least 4. * * Ensures: * The used pointer in 'b' is advanced by 4. */ void lwres_buffer_putmem(lwres_buffer_t *b, const unsigned char *base, unsigned int length); /**< * Copy 'length' bytes of memory at 'base' into 'b'. * * Requires: * 'b' is a valid buffer. * * 'base' points to 'length' bytes of valid memory. * */ void lwres_buffer_getmem(lwres_buffer_t *b, unsigned char *base, unsigned int length); /**< * Copy 'length' bytes of memory from 'b' into 'base'. * * Requires: * 'b' is a valid buffer. * * 'base' points to at least 'length' bytes of valid memory. * * 'b' have at least 'length' bytes remaining. */ LWRES_LANG_ENDDECLS #endif /* LWRES_LWBUFFER_H */
Save File
Cancel