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Fix COMP page trailer layout for SAS7BDAT files #423

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Fix COMP page trailer layout for SAS7BDAT files #423

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12 changes: 8 additions & 4 deletions src/sas/readstat_sas7bdat_write.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1028,6 +1028,10 @@ static readstat_error_t sas7bdat_write_comp_page(readstat_writer_t *writer, sas7
int64_t rows_on_first_page = 0;
int64_t i;

/* SAS lays out the COMP page within at most 0x7FFF bytes, as the field
* at phs-2 is a signed 16-bit value, and zero-fills the rest. */
size_t region = ctx->page_size < 0x7FFF ? ctx->page_size : 0x7FFF;

for (i=first_page->first; i<first_page->first+first_page->count; i++) {
if (ctx->subheaders[i]->is_row_data)
rows_on_first_page++;
Expand All @@ -1039,10 +1043,10 @@ static readstat_error_t sas7bdat_write_comp_page(readstat_writer_t *writer, sas7
w2(&buffer[ctx->phs-8], SAS_PAGE_TYPE_COMP);
w2(&buffer[ctx->phs-6], ctx->total_pages);
w2(&buffer[ctx->phs-4], 1);
w2(&buffer[ctx->phs-2], ctx->page_size - ctx->phs - ctx->sps - 2);
buffer[ctx->page_size-7] = rows_on_first_page & 0xFF;
buffer[ctx->page_size-6] = 1;
w2(&buffer[ctx->page_size-2], first_page->count);
w2(&buffer[ctx->phs-2], region - ctx->phs - ctx->sps - (10 - ctx->int_len));
buffer[region - ctx->int_len - 3] = rows_on_first_page & 0xFF;
buffer[region - ctx->int_len - 2] = 1;
w2(&buffer[region-2], first_page->count);

return readstat_write_bytes(writer, buffer, ctx->page_size);
}
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