Added a function for setting the I/O semantics on a Coffee file descriptor. Changed the configuration parameters slightly and updated the platform definitions to reflect this change.
This commit is contained in:
Nicolas Tsiftes
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@ -32,7 +32,13 @@
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/**
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* \file
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* Coffee: A flash file system for memory-constrained sensor systems.
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* Coffee: A file system for a variety of storage types in
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* memory-constrained devices.
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*
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* For further information, see "Enabling Large-Scale Storage in
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* Sensor Networks with the Coffee File System" in the proceedings
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* of ACM/IEEE IPSN 2009.
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*
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* \author
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* Nicolas Tsiftes <nvt@sics.se>
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*/
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@ -53,14 +59,35 @@
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#include "cfs-coffee-arch.h"
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#include "cfs/cfs-coffee.h"
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#ifndef COFFEE_CONF_APPEND_ONLY
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#define COFFEE_APPEND_ONLY 0
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#else
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#define COFFEE_APPEND_ONLY COFFEE_CONF_APPEND_ONLY
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#if COFFEE_MICRO_LOGS
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#error "Cannot have COFFEE_APPEND_ONLY when COFFEE_MICRO_LOGS is set."
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/* Micro logs enable modifications on storage types that do not support
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in-place updates. This applies primarily to flash memories. */
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#ifndef COFFEE_MICRO_LOGS
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#define COFFEE_MICRO_LOGS 1
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#endif
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#define COFFEE_MICRO_LOGS 0
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/* If the files are expected to be appended to only, this parameter
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can be set to save some code space. */
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#ifndef COFFEE_APPEND_ONLY
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#define COFFEE_APPEND_ONLY 0
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#endif
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#if COFFEE_MICRO_LOGS && COFFEE_APPEND_ONLY
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#error "Cannot have COFFEE_APPEND_ONLY set when COFFEE_MICRO_LOGS is set."
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#endif
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/* I/O semantics can be set on file descriptors in order to optimize
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file access on certain storage types. */
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#ifndef COFFEE_IO_SEMANTICS
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#define COFFEE_IO_SEMANTICS 0
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#endif
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/*
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* Prevent sectors from being erased directly after file removal.
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* This will level the wear across sectors better, but may lead
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* to longer garbage collection procedures.
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*/
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#ifndef COFFEE_EXTENDED_WEAR_LEVELLING
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#define COFFEE_EXTENDED_WEAR_LEVELLING 1
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#endif
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#if COFFEE_START & (COFFEE_SECTOR_SIZE - 1)
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@ -149,6 +176,9 @@ struct file_desc {
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cfs_offset_t offset;
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struct file *file;
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uint8_t flags;
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#ifdef COFFEE_IO_SEMANTICS
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uint8_t io_flags;
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#endif
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};
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/* The file header structure mimics the representation of file headers
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@ -579,7 +609,7 @@ remove_by_page(coffee_page_t page, int remove_log, int close_fds,
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}
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}
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#if !COFFEE_CONF_EXTENDED_WEAR_LEVELLING
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#if !COFFEE_EXTENDED_WEAR_LEVELLING
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if(gc_allowed) {
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collect_garbage(GC_RELUCTANT);
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}
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@ -1137,6 +1167,9 @@ cfs_write(int fd, const void *buf, unsigned size)
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file = fdp->file;
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/* Attempt to extend the file if we try to write past the end. */
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#ifdef COFFEE_IO_SEMANTICS
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if(!(fdp->io_flags & CFS_COFFEE_IO_FIRM_SIZE)) {
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#endif
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while(size + fdp->offset + sizeof(struct file_header) >
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(file->max_pages * COFFEE_PAGE_SIZE)) {
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if(merge_log(file->page, 1) < 0) {
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@ -1145,9 +1178,17 @@ cfs_write(int fd, const void *buf, unsigned size)
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file = fdp->file;
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PRINTF("Extended the file at page %u\n", (unsigned)file->page);
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}
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#ifdef COFFEE_IO_SEMANTICS
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}
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#endif
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#if COFFEE_MICRO_LOGS
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#if COFFEE_IO_SEMANTICS
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if(!(fdp->io_flags & CFS_COFFEE_IO_TOGGLE_ONLY) &&
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(FILE_MODIFIED(file) || fdp->offset < file->end)) {
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#else
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if(FILE_MODIFIED(file) || fdp->offset < file->end) {
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#endif
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for(bytes_left = size; bytes_left > 0;) {
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lp.offset = fdp->offset;
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lp.buf = buf;
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@ -1280,6 +1321,20 @@ cfs_coffee_configure_log(const char *filename, unsigned log_size,
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return 0;
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}
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/*---------------------------------------------------------------------------*/
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#ifdef COFFEE_IO_SEMANTICS
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int
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cfs_coffee_set_io_semantics(int fd, unsigned flags)
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{
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if(!FD_VALID(fd)) {
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return -1;
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}
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coffee_fd_set[fd].io_flags |= flags;
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return 0;
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}
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#endif
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/*---------------------------------------------------------------------------*/
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int
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cfs_coffee_format(void)
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{
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@ -40,6 +40,29 @@
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#include "cfs.h"
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/**
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* Instruct Coffee that the access pattern to this file is adapted to
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* flash I/O semantics by design, and Coffee should therefore not
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* invoke its own micro logs when file modifications occur.
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*
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* This semantical I/O setting is useful when implementing flash storage
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* algorithms on top of Coffee.
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*
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* \sa cfs_coffee_set_io_semantics()
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*/
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#define CFS_COFFEE_IO_TOGGLE_ONLY 0x1
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/**
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* Instruct Coffee not to attempt to extend the file when there is
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* an attempt to write past the reserved file size.
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*
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* A case when this is necessary is when the file has a firm size limit,
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* and a safeguard is needed to protect against writes beyond this limit.
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*
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* \sa cfs_coffee_set_io_semantics()
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*/
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#define CFS_COFFEE_IO_FIRM_SIZE 0x2
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/**
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* \file
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* Header for the Coffee file system.
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@ -65,9 +88,9 @@ int cfs_coffee_reserve(const char *name, cfs_offset_t size);
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/**
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* \brief Configure the on-demand log file.
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* \param file
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* \param log_size
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* \param log_entry_size
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* \param file The filename.
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* \param log_size The total log size.
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* \param log_entry_size The log entry size.
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* \return 0 on success, -1 on failure.
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*
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* When file data is first modified, Coffee creates a micro log for the
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@ -78,6 +101,21 @@ int cfs_coffee_reserve(const char *name, cfs_offset_t size);
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int cfs_coffee_configure_log(const char *file, unsigned log_size,
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unsigned log_entry_size);
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/**
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* \brief Set the I/O semantics for accessing a file.
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*
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* \param fd The file descriptor through which the file is accessed.
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* \param flags A bit vector of flags.
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*
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* Coffee is used on a wide range of storage types, and the default
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* I/O file semantics may not be optimal for the access pattern
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* of a certain file. Hence, this functions allows programmers to
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* switch the /O semantics on a file that is accessed through a
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* particular file descriptor.
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*
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*/
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int cfs_coffee_set_io_semantics(int fd, unsigned flags);
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/**
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* \brief Format the storage area assigned to Coffee.
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* \return 0 on success, -1 on failure.
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@ -55,6 +55,7 @@
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#define COFFEE_LOG_SIZE 8192
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#define COFFEE_LOG_TABLE_LIMIT 256
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#define COFFEE_MICRO_LOGS 0
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#define COFFEE_IO_SEMANTICS 1
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#define COFFEE_WRITE(buf, size, offset) \
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xmem_pwrite((char *)(buf), (size), COFFEE_START + (offset))
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@ -55,6 +55,8 @@
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#define COFFEE_DYN_SIZE 4*1024
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#define COFFEE_LOG_SIZE 1024
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#define COFFEE_IO_SEMANTICS 1
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#define COFFEE_APPEND_ONLY 0
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#define COFFEE_MICRO_LOGS 1
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/* Flash operations. */
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