--- /dev/null
+/* SPDX-License-Identifier: LGPL-2.1+ */
+/* Copyright (C) 2022 Kent Overstreet */
+
+#ifndef _BCACHEFS_PRINTBUF_H
+#define _BCACHEFS_PRINTBUF_H
+
+/*
+ * Printbufs: Simple strings for printing to, with optional heap allocation
+ *
+ * This code has provisions for use in userspace, to aid in making other code
+ * portable between kernelspace and userspace.
+ *
+ * Basic example:
+ * struct printbuf buf = PRINTBUF;
+ *
+ * prt_printf(&buf, "foo=");
+ * foo_to_text(&buf, foo);
+ * printk("%s", buf.buf);
+ * printbuf_exit(&buf);
+ *
+ * Or
+ * struct printbuf buf = PRINTBUF_EXTERN(char_buf, char_buf_size)
+ *
+ * We can now write pretty printers instead of writing code that dumps
+ * everything to the kernel log buffer, and then those pretty-printers can be
+ * used by other code that outputs to kernel log, sysfs, debugfs, etc.
+ *
+ * Memory allocation: Outputing to a printbuf may allocate memory. This
+ * allocation is done with GFP_KERNEL, by default: use the newer
+ * memalloc_*_(save|restore) functions as needed.
+ *
+ * Since no equivalent yet exists for GFP_ATOMIC/GFP_NOWAIT, memory allocations
+ * will be done with GFP_NOWAIT if printbuf->atomic is nonzero.
+ *
+ * It's allowed to grab the output buffer and free it later with kfree() instead
+ * of using printbuf_exit(), if the user just needs a heap allocated string at
+ * the end.
+ *
+ * Memory allocation failures: We don't return errors directly, because on
+ * memory allocation failure we usually don't want to bail out and unwind - we
+ * want to print what we've got, on a best-effort basis. But code that does want
+ * to return -ENOMEM may check printbuf.allocation_failure.
+ *
+ * Indenting, tabstops:
+ *
+ * To aid is writing multi-line pretty printers spread across multiple
+ * functions, printbufs track the current indent level.
+ *
+ * printbuf_indent_push() and printbuf_indent_pop() increase and decrease the current indent
+ * level, respectively.
+ *
+ * To use tabstops, set printbuf->tabstops[]; they are in units of spaces, from
+ * start of line. Once set, prt_tab() will output spaces up to the next tabstop.
+ * prt_tab_rjust() will also advance the current line of text up to the next
+ * tabstop, but it does so by shifting text since the previous tabstop up to the
+ * next tabstop - right justifying it.
+ *
+ * Make sure you use prt_newline() instead of \n in the format string for indent
+ * level and tabstops to work corretly.
+ *
+ * Output units: printbuf->units exists to tell pretty-printers how to output
+ * numbers: a raw value (e.g. directly from a superblock field), as bytes, or as
+ * human readable bytes. prt_units() obeys it.
+ */
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+
+enum printbuf_si {
+ PRINTBUF_UNITS_2, /* use binary powers of 2^10 */
+ PRINTBUF_UNITS_10, /* use powers of 10^3 (standard SI) */
+};
+
+#define PRINTBUF_INLINE_TABSTOPS 6
+
+struct printbuf {
+ char *buf;
+ unsigned size;
+ unsigned pos;
+ unsigned last_newline;
+ unsigned last_field;
+ unsigned indent;
+ /*
+ * If nonzero, allocations will be done with GFP_ATOMIC:
+ */
+ u8 atomic;
+ bool allocation_failure:1;
+ bool heap_allocated:1;
+ enum printbuf_si si_units:1;
+ bool human_readable_units:1;
+ bool has_indent_or_tabstops:1;
+ bool suppress_indent_tabstop_handling:1;
+ u8 nr_tabstops;
+
+ /*
+ * Do not modify directly: use printbuf_tabstop_add(),
+ * printbuf_tabstop_get()
+ */
+ u8 cur_tabstop;
+ u8 _tabstops[PRINTBUF_INLINE_TABSTOPS];
+};
+
+int bch2_printbuf_make_room(struct printbuf *, unsigned);
+__printf(2, 3) void bch2_prt_printf(struct printbuf *out, const char *fmt, ...);
+__printf(2, 0) void bch2_prt_vprintf(struct printbuf *out, const char *fmt, va_list);
+const char *bch2_printbuf_str(const struct printbuf *);
+void bch2_printbuf_exit(struct printbuf *);
+
+void bch2_printbuf_tabstops_reset(struct printbuf *);
+void bch2_printbuf_tabstop_pop(struct printbuf *);
+int bch2_printbuf_tabstop_push(struct printbuf *, unsigned);
+
+void bch2_printbuf_indent_add(struct printbuf *, unsigned);
+void bch2_printbuf_indent_sub(struct printbuf *, unsigned);
+
+void bch2_prt_newline(struct printbuf *);
+void bch2_prt_tab(struct printbuf *);
+void bch2_prt_tab_rjust(struct printbuf *);
+
+void bch2_prt_bytes_indented(struct printbuf *, const char *, unsigned);
+void bch2_prt_human_readable_u64(struct printbuf *, u64);
+void bch2_prt_human_readable_s64(struct printbuf *, s64);
+void bch2_prt_units_u64(struct printbuf *, u64);
+void bch2_prt_units_s64(struct printbuf *, s64);
+void bch2_prt_string_option(struct printbuf *, const char * const[], size_t);
+void bch2_prt_bitflags(struct printbuf *, const char * const[], u64);
+void bch2_prt_bitflags_vector(struct printbuf *, const char * const[],
+ unsigned long *, unsigned);
+
+/* Initializer for a heap allocated printbuf: */
+#define PRINTBUF ((struct printbuf) { .heap_allocated = true })
+
+/* Initializer a printbuf that points to an external buffer: */
+#define PRINTBUF_EXTERN(_buf, _size) \
+((struct printbuf) { \
+ .buf = _buf, \
+ .size = _size, \
+})
+
+/*
+ * Returns size remaining of output buffer:
+ */
+static inline unsigned printbuf_remaining_size(struct printbuf *out)
+{
+ return out->pos < out->size ? out->size - out->pos : 0;
+}
+
+/*
+ * Returns number of characters we can print to the output buffer - i.e.
+ * excluding the terminating nul:
+ */
+static inline unsigned printbuf_remaining(struct printbuf *out)
+{
+ return out->pos < out->size ? out->size - out->pos - 1 : 0;
+}
+
+static inline unsigned printbuf_written(struct printbuf *out)
+{
+ return out->size ? min(out->pos, out->size - 1) : 0;
+}
+
+/*
+ * Returns true if output was truncated:
+ */
+static inline bool printbuf_overflowed(struct printbuf *out)
+{
+ return out->pos >= out->size;
+}
+
+static inline void printbuf_nul_terminate(struct printbuf *out)
+{
+ bch2_printbuf_make_room(out, 1);
+
+ if (out->pos < out->size)
+ out->buf[out->pos] = 0;
+ else if (out->size)
+ out->buf[out->size - 1] = 0;
+}
+
+/* Doesn't call bch2_printbuf_make_room(), doesn't nul terminate: */
+static inline void __prt_char_reserved(struct printbuf *out, char c)
+{
+ if (printbuf_remaining(out))
+ out->buf[out->pos] = c;
+ out->pos++;
+}
+
+/* Doesn't nul terminate: */
+static inline void __prt_char(struct printbuf *out, char c)
+{
+ bch2_printbuf_make_room(out, 1);
+ __prt_char_reserved(out, c);
+}
+
+static inline void prt_char(struct printbuf *out, char c)
+{
+ __prt_char(out, c);
+ printbuf_nul_terminate(out);
+}
+
+static inline void __prt_chars_reserved(struct printbuf *out, char c, unsigned n)
+{
+ unsigned i, can_print = min(n, printbuf_remaining(out));
+
+ for (i = 0; i < can_print; i++)
+ out->buf[out->pos++] = c;
+ out->pos += n - can_print;
+}
+
+static inline void prt_chars(struct printbuf *out, char c, unsigned n)
+{
+ bch2_printbuf_make_room(out, n);
+ __prt_chars_reserved(out, c, n);
+ printbuf_nul_terminate(out);
+}
+
+static inline void prt_bytes(struct printbuf *out, const void *b, unsigned n)
+{
+ unsigned i, can_print;
+
+ bch2_printbuf_make_room(out, n);
+
+ can_print = min(n, printbuf_remaining(out));
+
+ for (i = 0; i < can_print; i++)
+ out->buf[out->pos++] = ((char *) b)[i];
+ out->pos += n - can_print;
+
+ printbuf_nul_terminate(out);
+}
+
+static inline void prt_str(struct printbuf *out, const char *str)
+{
+ prt_bytes(out, str, strlen(str));
+}
+
+static inline void prt_str_indented(struct printbuf *out, const char *str)
+{
+ bch2_prt_bytes_indented(out, str, strlen(str));
+}
+
+static inline void prt_hex_byte(struct printbuf *out, u8 byte)
+{
+ bch2_printbuf_make_room(out, 2);
+ __prt_char_reserved(out, hex_asc_hi(byte));
+ __prt_char_reserved(out, hex_asc_lo(byte));
+ printbuf_nul_terminate(out);
+}
+
+static inline void prt_hex_byte_upper(struct printbuf *out, u8 byte)
+{
+ bch2_printbuf_make_room(out, 2);
+ __prt_char_reserved(out, hex_asc_upper_hi(byte));
+ __prt_char_reserved(out, hex_asc_upper_lo(byte));
+ printbuf_nul_terminate(out);
+}
+
+/**
+ * printbuf_reset - re-use a printbuf without freeing and re-initializing it:
+ */
+static inline void printbuf_reset(struct printbuf *buf)
+{
+ buf->pos = 0;
+ buf->allocation_failure = 0;
+ buf->indent = 0;
+ buf->nr_tabstops = 0;
+ buf->cur_tabstop = 0;
+}
+
+/**
+ * printbuf_atomic_inc - mark as entering an atomic section
+ */
+static inline void printbuf_atomic_inc(struct printbuf *buf)
+{
+ buf->atomic++;
+}
+
+/**
+ * printbuf_atomic_inc - mark as leaving an atomic section
+ */
+static inline void printbuf_atomic_dec(struct printbuf *buf)
+{
+ buf->atomic--;
+}
+
+#endif /* _BCACHEFS_PRINTBUF_H */
projects / bcachefs-tools-debian / blobdiff