librdata - Read and write R data frames from C
Originally part of ReadStat, librdata is a small C library for reading and writing R data frames.
Features:
- Read both RData and RDS formats
- Read compressed files (requires bzip2, zlib, and lzma)
- Write factors, timestamps, logical vectors, and more
Installation
./autogen.sh
./configure
make
make install
If you're on Mac and see errors about AM_ICONV when you run ./autogen.sh,
you'll need to install gettext.
Language bindings
- Python: pyreadr
Read API
Example usage:
#include "rdata.h"
static int handle_table(const char *name, void *ctx) {
printf("Read table: %s\n", name);
return 0; /* non-zero to abort processing */
}
// Called once for all columns with the following caveats:
// * `name` is NULL for some columns (see handle_column_name below)
// * `data` is NULL for text columns (see handle_text_value below)
static int handle_column(const char *name, rdata_type_t type,
void *data, long count, void *ctx) {
/* Do something... */
return 0;
}
// Some column names appear in the file after the data
static int handle_column_name(const char *name, int index, void *ctx) {
if (debug) printf("Read column name: %s\n", name);
/* Do something... */
return 0;
}
// Called once per row for a text column
static int handle_text_value(const char *value, int index, void *ctx) {
/* Do something... */
return 0;
}
// Called for factor variables, once for each level
static int handle_value_label(const char *value, int index, void *ctx) {
/* Do something... */
return 0;
}
rdata_parser_t *parser = rdata_parser_init();
rdata_set_table_handler(parser, &handle_table);
rdata_set_column_handler(parser, &handle_column);
rdata_set_text_value_handler(parser, &handle_text_value);
rdata_set_value_label_handler(parser, &handle_value_label);
rdata_parse(parser, "/path/to/something.rdata", NULL);See rdata.h for the full API.
Write API
Example usage:
#include "rdata.h"
static ssize_t write_data(const void *bytes, size_t len, void *ctx) {
int fd = *(int *)ctx;
return write(fd, bytes, len);
}
int row_count = 3;
int fd = open("/path/to/somewhere.rdata", O_CREAT | O_WRONLY, 0644);
rdata_writer_t *writer = rdata_writer_init(&write_data, RDATA_WORKSPACE);
rdata_column_t *col1 = rdata_add_column(writer, "column1", RDATA_TYPE_REAL);
rdata_column_t *col2 = rdata_add_column(writer, "column2", RDATA_TYPE_STRING);
rdata_begin_file(writer, &fd);
rdata_begin_table(writer, "my_table");
rdata_begin_column(writer, col1, row_count);
rdata_append_real_value(writer, 0.0);
rdata_append_real_value(writer, 100.0);
rdata_append_real_value(writer, NAN);
rdata_end_column(writer, col1);
rdata_begin_column(writer, col2, row_count);
rdata_append_string_value(writer, "hello");
rdata_append_string_value(writer, "goodbye");
rdata_append_string_value(writer, NULL);
rdata_end_column(writer, col2);
rdata_end_table(writer, row_count, "My data set");
rdata_end_file(writer);
close(fd);
See rdata.h for the full API.